JP4687645B2 - Magnetic recording medium, magnetic recording / reproducing apparatus, and concave / convex depth inspection method for concave / convex pattern - Google Patents

Description

  The present invention relates to a magnetic recording medium having a recording layer divided into a large number of recording elements in a predetermined concavo-convex pattern, a magnetic recording / reproducing apparatus including the recording layer, and a method for inspecting the concave portion depth of the concavo-convex pattern.

  2. Description of the Related Art Conventionally, magnetic recording media have been remarkably improved in surface recording density through improvements such as miniaturization of magnetic particles constituting a recording layer, change of materials, and miniaturization of head processing. In recent years, a perpendicular recording type magnetic recording medium in which a soft magnetic layer is provided between a recording layer and a substrate is becoming widespread, and further improvement in surface recording density is expected in the future.

  However, problems such as erroneous recording of information on other tracks adjacent to the track to be recorded due to the processing limit of the magnetic head, the spread of the recording magnetic field of the magnetic head, and crosstalk at the time of reproduction have become obvious. The improvement of the surface recording density by the improved method has reached the limit.

  Therefore, as a candidate for a magnetic recording medium capable of further improving the surface recording density, a discrete track medium in which the recording layer is divided into a number of recording elements in the shape of a track in the data area, or a track in the circumferential direction as well. Patterned media divided into a large number of divided recording elements has been proposed. In order to improve the servo information recording efficiency, it has also been proposed to form a recording layer in the shape of a servo pattern in the servo area. Such discrete track media and patterned media are also expected to be synergistically improved in surface recording density by adopting a perpendicular recording type.

  As a method of dividing the recording layer into a large number of recording elements, it has been proposed to use a dry etching technique used in the semiconductor manufacturing field (see, for example, Patent Document 1).

  In order to obtain good recording / reproducing characteristics, it is considered preferable to divide the recording layer by etching the recording layer to the surface on the substrate side. On the other hand, in order to obtain good recording / reproducing characteristics, it is considered preferable not to etch the soft magnetic layer.

  Therefore, it is important to be able to accurately control the recess depth of the concavo-convex pattern of the recording layer and to accurately confirm the recess depth of the concavo-convex pattern of the etched recording layer. If a TEM (transmission electron microscope) or SEM (scanning electron microscope) is used, the depth of the recess can be confirmed.

JP-A-9-97419

  However, in the case of using TEM or SEM, it is necessary to produce a sample by cutting an object to be inspected having a recording layer with a concavo-convex pattern. On the other hand, in terms of quality control, it is preferable to be able to inspect products that are actually shipped or intermediate products in the manufacturing process, and there is a need to check the depth of the concave portions of the concave-convex pattern of the recording layer in a non-destructive manner. Furthermore, when using TEM or SEM, there is also a problem that the time required for sample preparation and sample observation is long.

  The present invention has been made in view of the above problems, and is a magnetic recording medium capable of quickly and non-destructively confirming the recess depth of the concavo-convex pattern of the recording layer, a magnetic recording / reproducing apparatus including the same, and an inspection target It is an object of the present invention to provide a method for inspecting the concave / convex pattern of the concave / convex pattern, which can quickly confirm the concave / convex depth of the concave / convex pattern of the recording layer without cutting the body.

  The present invention relates to a substrate, a soft magnetic layer formed on the substrate, a recording layer formed on the soft magnetic layer and divided into a plurality of recording elements in a predetermined uneven pattern, and a thickness. An intermediate magnetic layer formed between the recording layer and the soft magnetic layer, the magnitude of the direction nucleation magnetic field being different from the magnitude of the nucleation magnetic field in the thickness direction of the recording layer, and the bottom surface of the concave portion of the concave-convex pattern Is achieved by a magnetic recording medium positioned in the region of the intermediate magnetic layer.

  The present invention also relates to a substrate, a soft magnetic layer formed on the substrate, a recording layer formed on the soft magnetic layer and divided into a plurality of recording elements in a predetermined uneven pattern, and the thickness direction. The nucleation magnetic field of the recording layer differs from the nucleation magnetic field in the thickness direction of the recording layer on the surface on the recording layer side of the object to be inspected including the intermediate magnetic layer formed between the recording layer and the soft magnetic layer. A magnetic Kerr effect characteristic measuring step for measuring the magnetic Kerr effect characteristic by irradiating light and measuring the reflected light, and a concave part for determining the position of the bottom of the concave part of the concave and convex pattern based on the measurement result of the magnetic Kerr effect characteristic The above-described object is achieved by a method for inspecting a recess depth of a concavo-convex pattern including a depth discrimination step.

  The inventors have found that the nucleation magnetic field in the thickness direction is different from the nucleation magnetic field in the thickness direction of the recording layer between the recording layer and the soft magnetic layer which are divided into a large number of recording elements by the concavo-convex pattern. By providing the magnetic layer, the magnetic recording medium (inspected object) is irradiated depending on whether the bottom surface of the concave portion of the concave-convex pattern is located in the intermediate magnetic layer region or not in the intermediate magnetic layer region. It has been found that there is a difference in the magnetic Kerr effect characteristics of the emitted light.

  When the bottom surface of the concave portion of the concavo-convex pattern is located in the recording layer region, only the magnetic characteristics of the recording layer are reflected in the magnetic Kerr effect characteristic, whereas the bottom surface of the concave portion of the concavo-convex pattern is the region of the intermediate magnetic layer. When the magnetic Kerr effect characteristic is present, both the magnetic characteristic of the convex recording layer and the magnetic characteristic of the concave intermediate magnetic layer are reflected in the magnetic Kerr effect characteristic. Conceivable.

  Therefore, in the above magnetic recording medium, it is possible to quickly confirm whether or not the recording layer is divided without breaking.

  In addition, even if an undivided intermediate magnetic layer exists below the recording layer, the inventors suppress the saturation magnetic flux density of the intermediate magnetic layer to be smaller than the saturation magnetic flux density of the recording layer, thereby It has been found that noise from the intermediate magnetic layer is suppressed to a small level, and that the same recording / reproducing characteristics as when the intermediate magnetic layer is not present under the recording layer can be obtained.

  That is, the above-described object can be achieved by the following present invention.

(1) a substrate, a soft magnetic layer formed on the substrate, a recording layer formed on the soft magnetic layer and divided into a plurality of recording elements in a predetermined uneven pattern, and a thickness An intermediate magnetic layer formed between the recording layer and the soft magnetic layer, the magnitude of the direction nucleation magnetic field being different from the magnitude of the nucleation magnetic field in the thickness direction of the recording layer, A magnetic recording medium, wherein the bottom surface of the recess is located in the region of the intermediate magnetic layer.

(2) The magnetic recording medium according to (1), wherein the nucleation magnetic field in the thickness direction of the intermediate magnetic layer is smaller than the nucleation magnetic field in the thickness direction of the recording layer.

(3) The magnetic recording medium according to (1) or (2), wherein a saturation magnetic flux density of the intermediate magnetic layer is smaller than a saturation magnetic flux density of the recording layer.

(4) The magnetic recording medium according to (3), wherein a saturation magnetic flux density of the intermediate magnetic layer is 0.15 T or less.

(5) The magnetic recording medium according to any one of (1) to (4), further comprising a translucent filler filled in the concave portion of the concave-convex pattern.

(6) The magnetic recording medium according to (5), further comprising a translucent protective layer covering the upper surface of the recording element and the upper surface of the filler.

(7) A magnetic recording / reproducing apparatus comprising the magnetic recording medium according to any one of (1) to (6).

(8) Substrate, soft magnetic layer formed on the substrate, recording layer formed on the soft magnetic layer and divided into a large number of recording elements in a predetermined uneven pattern, and a nucleus in the thickness direction The surface on the recording layer side of the object to be inspected includes an intermediate magnetic layer formed between the recording layer and the soft magnetic layer, the magnitude of the forming magnetic field being different from the magnitude of the nucleation magnetic field in the thickness direction of the recording layer The magnetic Kerr effect characteristic measuring step of measuring the magnetic Kerr effect characteristic by irradiating the light and measuring the reflected light, and determining the position of the bottom surface of the concave portion of the concave / convex pattern based on the measurement result of the magnetic Kerr effect characteristic And a concave portion depth determining step. The concave portion concave portion depth inspection method comprising:

(9) In (8), in the recess depth determining step, it is determined whether or not the bottom surface of the recess of the uneven pattern is located in the region of the intermediate magnetic layer based on the measurement result of the magnetic Kerr effect characteristic. A method for inspecting a recess depth of a concavo-convex pattern, comprising:

(10) In (8) or (9), in the concave portion depth determining step, the bottom surface of the concave portion of the concave / convex pattern is the region of the recording layer, the intermediate magnetic layer based on the measurement result of the magnetic Kerr effect characteristic. A method for inspecting a recess depth of a concavo-convex pattern, comprising determining whether the region is located in a region or a region of the soft magnetic layer.

(11) In any one of (8) to (10), in the magnetic Kerr effect characteristic measurement step, an external magnetic field is applied to the object to be inspected while varying the magnitude thereof, and the Kerr rotation angle is set as the magnetic Kerr effect characteristic. And determining the position of the bottom surface of the concave portion of the concave / convex pattern based on a hysteresis curve indicating the relationship between the magnitude of the external magnetic field and the Kerr rotation angle in the concave depth determining step. Recess depth inspection method.

(12) In (11), it is determined whether or not the bottom surface of the recess is located in the region of the intermediate magnetic layer based on the presence or absence of a step portion of the hysteresis curve in the recess depth determination step. A method for inspecting the recess depth of the uneven pattern.

(13) The concave / convex pattern according to any one of (8) to (12), wherein the position of the bottom surface of the concave portion is determined based on the magnitude of a nucleation magnetic field obtained by measuring the magnetic Kerr effect characteristic. Recess depth inspection method.

  In the present application, the “recording layer divided into a large number of recording elements with a predetermined uneven pattern” means a recording layer in which a continuous recording layer is divided into a large number of recording elements with a predetermined pattern, for example, a track The term “recording layer” is used to include a recording layer that is partially formed on a substrate, such as a recording layer in which recording elements having a shape are continuous at the end or a recording layer in which a recording element has a spiral shape.

  Further, in the present application, the term “magnetic recording medium” is not limited to a hard disk or floppy (registered trademark) disk that uses only magnetism for recording and reading information, and MO (Magneto Optical) that uses both magnetism and light. The magneto-optical recording medium and the heat-assisted recording medium using both magnetism and heat are also used in the meaning.

  In this application, “the bottom surface of the concave portion of the concave / convex pattern is located in the region of the intermediate magnetic layer” means that when the bottom surface of the concave portion coincides with the top surface of the intermediate magnetic layer, the entire bottom surface of the concave portion is the intermediate magnetic layer. In the meaning including the case where it exists in the area | region in the middle of the thickness direction of this. The same applies to “the bottom surface of the concave portion of the concave / convex pattern is located in the region of the soft magnetic layer”.

  Further, in the present application, “the bottom surface of the concave portion of the concave / convex pattern is located in the region of the recording layer” means that the entire bottom surface of the concave portion is present in the middle region in the thickness direction of the recording layer, and The concave layer is not formed and the recording layer is a uniform continuous film. In other words, the recording layer is used in a meaning including the case where the bottom surface of the concave portion coincides with the upper surface of the recording layer.

  According to the present invention, a magnetic recording medium capable of quickly and non-destructively confirming the concave depth of the concave-convex pattern of the recording layer, a magnetic recording medium including the same, and the concave-convex pattern of the recording layer without cutting the object to be inspected are provided. A concave / convex depth inspection method for a concave / convex pattern that can quickly confirm the concave depth can be realized.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the magnetic recording / reproducing apparatus 1 according to the present embodiment is close to the magnetic recording medium 10 and the surface of the magnetic recording medium 10 for recording / reproducing data on the magnetic recording medium 10. The magnetic recording medium 10 is characterized in that the magnetic recording medium 10 has a floating magnetic head 2 installed so that it can float. Since other configurations are not considered particularly necessary for understanding the present embodiment, the description thereof will be omitted as appropriate.

  The magnetic recording medium 10 has a center hole, is fixed to the chuck 3 in the center hole, and is rotatable with the chuck 3. The magnetic head 2 is mounted near the tip of the arm 4, and the arm 4 is rotatably attached to the base 5. As a result, the magnetic head 2 is movable along an arc orbit along the radial direction of the magnetic recording medium 10 while flying close to the surface of the magnetic recording medium 10.

  The magnetic recording medium 10 is a disc-shaped perpendicular recording type discrete track medium. As shown in FIG. 2, the magnetic recording medium 10 includes a substrate 12, a soft magnetic layer 14 formed on the substrate 12, and a soft magnetic layer 14. And a nucleation magnetic field in the thickness direction of the recording layer 16 in which the magnitude of the nucleation magnetic field in the thickness direction Unlike the size, it includes an intermediate magnetic layer 18 formed between the recording layer 16 and the soft magnetic layer 14, and the bottom surface 20 </ b> A of the concave portion 20 of the concave / convex pattern is located in the region of the intermediate magnetic layer 18. The thickness direction is a direction perpendicular to the surface of the magnetic recording medium 10.

  The recording layer 16 is oriented so as to have magnetic anisotropy in a direction perpendicular to the surface. The recording layer 16 and the intermediate magnetic layer 18 are in contact with each other.

  The magnetic recording medium 10 also has a translucent filler 22 that fills the recesses 20 of the uneven pattern.

  Further, the magnetic recording medium 10 has a translucent protective layer 24 that covers the upper surface of the recording element 16 </ b> A and the upper surface of the filler 20.

  Note that a light-transmitting lubricating layer 26 is formed on the protective layer 24. An underlayer 28 is formed between the intermediate magnetic layer 18 and the soft magnetic layer 14.

  Since other configurations are not considered particularly necessary for understanding the present embodiment, the description thereof will be omitted as appropriate.

The surface of the substrate 12 on the recording layer 16 side is mirror-polished. As the material of the substrate 22, a nonmagnetic material such as glass, NiP-coated Al alloy, Si, Al ₂ O ₃ or the like can be used.

  The soft magnetic layer 14 has a thickness of 50 to 300 nm. As a material of the soft magnetic layer 14, an Fe alloy, a Co amorphous alloy, ferrite, or the like can be used. The soft magnetic layer 14 may have a laminated structure of a soft magnetic layer and a nonmagnetic layer. The nucleation magnetic field Hn in the thickness direction of the soft magnetic layer 14 is 0.01 to 0.15 kA / m, which is smaller than that of the recording layer 16 and the intermediate magnetic layer 18. The saturation magnetic flux density of the soft magnetic layer 14 is 1.2 to 1.8T.

The recording layer 16 has a thickness of 5 to 40 nm. As the material of the recording layer 16, an alloy containing Co and Cr, such as a CoCrPt alloy, an alloy containing Co and Pt, an alloy containing Co and Pd, an alloy containing Fe and Pt, an alloy containing Fe and Co, and a laminate thereof A material in which ferromagnetic particles such as CoPt are included in a matrix in an oxide material such as SiO ₂ can be used. The nucleation magnetic field Hnr in the thickness direction of the recording layer 16 is preferably 135 to 400 kA / m. The saturation magnetic flux density Bs of the recording layer 16 is preferably 0.3 to 1.0T.

  The recording elements 16A are formed in a concentric track shape in the data area and are formed at fine intervals in the radial direction, and FIG. 2 illustrates this. The recording element 16A is formed with a predetermined servo pattern in the servo area (not shown).

  The intermediate magnetic layer 18 has a thickness of 2 to 40 nm. The material of the intermediate magnetic layer 18 includes an alloy containing Co, an alloy containing Co and Pt, an alloy containing Fe, an alloy containing Fe and Co, an alloy containing Fe and Ni, an alloy containing Fe and N, Fe and Al. An alloy containing Fe, an alloy containing Fe and Pt, or the like can be used. The nucleation magnetic field Hn in the thickness direction of the intermediate magnetic layer 18 is smaller than that of the recording layer. The nucleation magnetic field Hnm in the thickness direction of the intermediate magnetic layer 18 is preferably 25 to 180 kA / m. The intermediate magnetic layer 18 also has a saturation magnetic flux density Bs lower than that of the recording layer 16. The saturation magnetic flux density Bs of the intermediate magnetic layer 18 is preferably 0.05 to 0.15T.

  The recess 20 is formed halfway in the thickness direction of the intermediate magnetic layer 18, and the entire bottom surface 20 </ b> A exists in a region in the middle of the thickness direction of the intermediate magnetic layer 18. The recess 20 is preferably formed such that the thickness of the portion below the bottom surface 20A of the intermediate magnetic layer 18 is 2 nm or more.

As a material of the filler 22, a light-transmitting material such as silicon oxide containing SiO ₂ as a main component, an oxide such as Al ₂ O ₃ or TiO ₂ , a nitride such as AlN, or a light-transmitting resin material is used. Can be used.

The protective layer 24 has a thickness of 1 to 5 nm. As a material of the protective layer 24, for example, a translucent hard carbon film called diamond-like carbon can be used. In the present application, the term “diamond-like carbon (hereinafter referred to as“ DLC ”)” is mainly composed of carbon, has an amorphous structure, and has a Vickers hardness measurement of about 2 × 10 ⁹ to 8 × 10 ¹⁰ Pa. It is used in the meaning of a material that exhibits hardness.

  The lubricating layer 26 has a thickness of 1 to 2 nm. As a material of the lubricating layer 26, PFPE (perfluoropolyether) or the like can be used.

  The underlayer 28 has a thickness of 2 to 40 nm. As the material of the underlayer 28, nonmagnetic CoCr alloy, Ti, Ru, a laminate of Ru and Ta, MgO, or the like can be used.

  Next, the operation of the magnetic recording medium 10 will be described.

  The magnetic recording medium 10 has good recording / reproducing characteristics because the bottom surface 20A of the concave portion 20 of the concave / convex pattern is located in the region of the intermediate magnetic layer 18 and the recording elements 16A of the recording layer 16 are divided.

  Although the non-divided intermediate magnetic layer 18 exists under the recording layer 16, the saturation magnetic flux density of the intermediate magnetic layer 18 is suppressed to be smaller than the saturation magnetic flux density of the recording layer 16. The noise from the intermediate magnetic layer 18 is suppressed to a small level, and the same recording / reproducing characteristics as when the intermediate magnetic layer 18 does not exist under the recording layer 16 can be obtained. This will be described in more detail in a simulation example described later.

  Further, since the intermediate magnetic layer 18 is not divided and the depth of the concave portion 20 is so shallow, the processing of the concave portion 20 is easy. Furthermore, since the depth of the recess 20 is shallow, it is easy to fill the recess 20 and flatten it.

  Further, in the magnetic recording medium 10, since the nucleation magnetic field Hn in the thickness direction of the intermediate magnetic layer 18 is smaller than the nucleation magnetic field Hn in the thickness direction of the recording layer 16, the magnetization reversal of the recording layer 16 during recording is smooth. It is.

  Further, the magnetic recording medium 10 includes an intermediate magnetic layer having a nucleation magnetic field Hn in the thickness direction smaller than that of the recording layer 16 between the recording layer 16 and the soft magnetic layer 14 divided into a large number of recording elements 16A in an uneven pattern. 18 is provided on the recording layer 16 side when the bottom surface 20A of the concave portion 20 of the concave / convex pattern is located in the region of the intermediate magnetic layer 18 and when it is not located in the region of the intermediate magnetic layer 18. Differences occur in the magnetic Kerr effect characteristics of the irradiated light.

  When the bottom surface 20A of the concave portion 20 of the concave / convex pattern is located in the region of the recording layer 16, only the magnetic characteristic of the recording layer 16 is reflected in the magnetic Kerr effect characteristic of the reflected light, whereas the bottom surface of the concave portion 20 of the concave / convex pattern When 20A is located in the region of the intermediate magnetic layer 18, both the magnetic characteristics of the convex recording layer 16 (recording element 16A) and the magnetic characteristics of the intermediate magnetic layer 18 of the concave 20 are reflected in the magnetic Kerr effect characteristics. Therefore, it is considered that such a difference in magnetic Kerr effect characteristics occurs.

  Therefore, the magnetic recording medium 10 can quickly and non-destructively confirm the depth of the concave portion 20 of the concave / convex pattern of the recording layer 16.

  Hereinafter, a method for inspecting the recess depth of the uneven pattern of the magnetic recording medium 10 will be described with reference to the flowchart of FIG.

  First, the surface of the magnetic recording medium 10 (inspected object) on the recording layer 16 side is irradiated with linearly polarized light and the reflected light is measured to measure the magnetic Kerr effect characteristic (S102).

  For example, by using a Kerr rotation angle measuring device 30 as shown in FIG. 4, the Kerr rotation angle θk is measured as the magnetic Kerr effect characteristic by applying the external magnetic field H to the magnetic recording medium 10 while changing the magnitude thereof. .

  Here, the configuration of the car rotation angle measurement device 30 will be briefly described.

  The Kerr rotation angle measuring device 30 includes a light source 30A that emits monochromatic laser light, a polarizer 30C for obtaining linearly polarized light, a half mirror 30E, a mirror 30F, and an electromagnet 30G, which are magnetized in this order. It is arranged on the optical path of an irradiation system for irradiating the recording medium 10 with laser light. Note that a hole is formed in the electromagnet 30G at a portion corresponding to the optical path of the irradiation system.

  Furthermore, the Kerr rotation angle measuring device 30 reaches the half mirror 30E via the electromagnet 30G and the mirror 30F, and reflects the reflected light from the magnetic recording medium 10 reflected in a direction different from the polarizer 30C in two directions depending on the polarization direction. A beam splitter 30H for splitting, an analyzer 30J on which polarized light in one direction is incident, an analyzer 30K on which polarized light in the other direction is incident, and the intensity of polarized light in each direction incident on the analyzers 30J and 30K Differential amplifier 30L for detecting the difference between the two.

  An external magnetic field is applied to the magnetic recording medium 10 while changing its magnitude in a direction perpendicular to the surface by the electromagnet 30D.

  By measuring the relationship between the difference in the intensity of polarized light detected by the differential amplifier 30L in each direction and the Kerr rotation angle θk in advance using a standard sample, the magnetic field is determined based on the detection value of the differential amplifier 30L. The Kerr rotation angle θk of the recording medium 10 (inspected object) can be obtained.

  Next, based on the measurement result of the magnetic Kerr effect characteristic, it is determined whether or not the bottom surface 20A of the concave portion 20 of the concave / convex pattern of the recording layer 16 is located in the region of the intermediate magnetic layer 18 (S104).

  For example, based on a hysteresis curve indicating the relationship between the magnitude of the external magnetic field H and the Kerr rotation angle θk, whether or not the bottom surface 20A of the concave portion 20 of the concave / convex pattern of the recording layer 16 is located in the region of the intermediate magnetic layer 18 is determined. Determine.

  When the bottom surface 20A of the recess 20 is located in the region of the intermediate magnetic layer 18 as shown in FIG. 2, the relationship between the magnitude of the external magnetic field H and the Kerr rotation angle θk is shown in FIG. A step S exists in the hysteresis curve shown. As shown in an enlarged view in FIG. 6, the nucleation magnetic field Hnm in the thickness direction of the intermediate magnetic layer 18, which is the magnitude of the external magnetic field H at which the intermediate magnetic layer 18 starts to reverse magnetization, is the thickness of the recording layer 16. This is because the saturation magnetic field Hsm in the thickness direction of the intermediate magnetic layer 18 exists between them, which is smaller than the nucleation magnetic field Hnr in the vertical direction.

  In the present application, the nucleation magnetic field Hn and the saturation magnetic field Hs are the externals corresponding to the intersections of the extension lines of the linear portion in the hysteresis curve showing the relationship between the magnitude of the external magnetic field H and the Kerr rotation angle θk as shown in FIG. Used to mean the magnitude of the magnetic field H. Further, the phrase “the nucleation magnetic field Hn and the saturation magnetic field Hs are large (or small)” means that the absolute values thereof are large (or small).

  Even when the nucleation magnetic field Hnm in the thickness direction of the intermediate magnetic layer 18 is larger than the nucleation magnetic field Hnr in the thickness direction of the recording layer 16, the saturation magnetic field Hsr in the thickness direction of the recording layer 16 does not exceed the intermediate magnetic layer 18. If it is smaller than the nucleation magnetic field Hnm in the thickness direction, a step S appears in the hysteresis curve as in FIG.

  On the other hand, when both the saturation magnetic field Hsr of the recording layer 16 and the saturation magnetic field Hsm of the intermediate magnetic layer 18 are larger than the nucleation magnetic field Hnr of the recording layer 16 and the nucleation magnetic field Hnm of the intermediate magnetic layer 18, FIG. As shown in FIG. 8, the step S does not appear in the hysteresis curve, and the nucleation magnetic field Hnm of the intermediate magnetic layer 18, the nucleation magnetic field Hnr of the recording layer 16, the saturation magnetic field Hsm of the intermediate magnetic layer 18 (or Three bent portions corresponding to the saturation magnetic field Hsr) of the recording layer 16 appear.

  In FIG. 7, when the value of the saturation magnetic field Hsm of the intermediate magnetic layer 18 and the nucleation magnetic field Hnr of the recording layer 16 are substantially equal, only one bent portion may appear as shown in FIG. is there. The same applies when the saturation magnetic field Hsr of the recording layer 16 and the nucleation magnetic field Hnm of the intermediate magnetic layer 18 are substantially equal in FIG.

  On the other hand, the bottom surface 20A of the recess 20 as shown in FIG. 14 is located in a region in the middle of the thickness direction of the recording layer 16, and no recess is formed, and the recording layer is a continuous film. In the case of a certain magnetic recording medium, only the magnetization state of the recording layer 16 is reflected in the Kerr rotation angle θk, and the magnetization state of the intermediate magnetic layer 18 is not reflected in the Kerr rotation angle θk. Therefore, as shown in FIG. There are no steps in the hysteresis curve showing the relationship between the magnitude of the magnetic field H and the Kerr rotation angle θk of the reflected light, and there are no multiple bent portions as shown in FIGS.

  Therefore, for example, by confirming that there is no step in the hysteresis curve, it is determined that the bottom surface 20A of the recess 20 is not located in the region of the intermediate magnetic layer 1, and it is confirmed that there is a step in the hysteresis curve. Thus, it can be determined that the bottom surface 20 </ b> A of the recess 20 is located in the region of the intermediate magnetic layer 18.

  Further, it is determined that the bottom surface 20A of the concave portion 20 is not located in the region of the intermediate magnetic layer 18 by confirming that there is only one bent portion in the region (positive region) where the external magnetic field in the hysteresis curve is positive. The bottom surface 20A of the recess 20 is located in the region of the intermediate magnetic layer 18 by confirming that there are three or two bent portions in the region where the external magnetic field in the hysteresis curve is positive (or a negative region). Can be determined. Thus, the position of the bottom surface 20A of the recess 20 can be determined based on the number of bent portions of the hysteresis curve.

  That is, the position of the bottom surface 20A of the concave portion 20 of the concave / convex pattern of the recording layer 16 can be quickly confirmed without destruction.

  When the nucleation magnetic field Hnm of the intermediate magnetic layer 18 is smaller than the nucleation magnetic field Hnr of the recording layer 16, the saturation magnetic field Hsm of the intermediate magnetic layer 18 and the nucleation magnetic field Hnr of the recording layer 16 are shown in FIG. When the values are almost equal (when only one bent portion appears), if the bottom surface 20A of the recess 20 is located in the region of the intermediate magnetic layer 18, the bending corresponding to the nucleation magnetic field Hnm of the intermediate magnetic layer 18 is obtained. And a bent portion corresponding to the nucleation magnetic field Hnr of the recording layer 16 appears if the bottom surface 20A of the concave portion 20 is located in the middle of the recording layer 16 in the thickness direction. The position of the bottom surface 20A of the recess 20 can be determined based on the magnitude of the magnetic field corresponding to.

  When the nucleation magnetic field Hnm of the intermediate magnetic layer 18 is larger than the nucleation magnetic field Hnr of the recording layer 16, the saturation magnetic field Hsr of the recording layer 16 and the nucleation magnetic field Hnm of the intermediate magnetic layer 18 are substantially equal. However, as shown in the hysteresis curve of FIG. 9, in the region where H is positive and θk is negative, only one bent portion corresponding to the nucleation magnetic field Hnr of the recording layer 16 appears, and the bottom surface 20A of the recess 20 is intermediate magnetic. If it is located in the region of the layer 18, one bent portion corresponding to the saturation magnetic field Hsm of the intermediate magnetic layer 18 appears in a region where H and θk are positive. On the other hand, if the bottom surface 20A of the recess 20 is located in the middle region in the thickness direction of the recording layer 16, the magnetic characteristics of the intermediate magnetic layer 18 are not reflected in θk, and therefore the recording layer in the region where H and θk are positive. A bent portion corresponding to 16 saturation magnetic fields Hsr appears. Accordingly, even in such a case, the position of the bottom surface 20A of the recess 20 can be determined based on the hysteresis curve.

  The operator may visually check the presence or absence of a step portion in the hysteresis curve, the number of bent portions, and the magnitude of the magnetic field corresponding to the bent portion. Further, the Kerr rotation angle measuring device 30 may be provided with an image processing device so that the presence or absence of a step portion of the hysteresis curve, the number of bent portions, and the magnitude of the magnetic field corresponding to the bent portion can be automatically checked. Good.

  As described above, the magnetic recording medium 10 can quickly and non-destructively confirm the depth of the concave portion 20 of the concave / convex pattern of the recording layer 16, so that an extraction inspection and a total inspection of products actually shipped can be performed. Contributes to improving the reliability of quality control. For example, a product in which the bottom surface 20 </ b> A of the recess 20 is located in the region of the intermediate magnetic layer 18 can be a non-defective product, and the other can be a defective product.

  The intermediate magnetic layer 18 is divided by the recess 20 and the bottom surface 20A of the recess 20 is located in the middle of the thickness direction of the underlayer 28, or the bottom surface 20A of the recess 20 is the thickness of the soft magnetic layer 14. Even in the region in the middle of the direction, the nonmagnetic characteristics of the underlayer 28 and the magnetization state of the soft magnetic layer 14 as well as the magnetization state of the recording layer 16 are reflected in the measured Kerr rotation angle θk, respectively. Since the magnetic Kerr effect characteristic peculiar to the above case is shown, the bottom surface 20A of the recess 20 is located in the middle region in the thickness direction of the underlayer 28 and in the middle region in the thickness direction of the soft magnetic layer 14. It is possible to determine.

  For example, when the bottom surface 20 </ b> A of the recess 20 is located in an intermediate region in the thickness direction of the underlayer 28, the Kerr rotation is performed with respect to the case where the bottom surface 20 </ b> A of the recess 20 is located in the region of the intermediate magnetic layer 18. Since the angle θk is measured to be small, it can be determined that the bottom surface 20 </ b> A of the recess 20 is located in an intermediate region in the thickness direction of the foundation layer 28.

  In addition, the nucleation magnetic field Hn obtained by measuring the magnetic Kerr effect characteristic can be obtained by previously grasping the nucleation magnetic field Hn in the thickness direction of each of the recording layer 16, the intermediate magnetic layer 18, and the soft magnetic layer 14. Based on this, it is also possible to determine which of these layers the bottom surface 20A of the recess 20 is located in.

  For example, the nucleation magnetic field Hn in the thickness direction of the soft magnetic layer 14 is smaller than the nucleation magnetic field Hn in the thickness direction of the recording layer 16 and the intermediate magnetic layer 18, and a bent portion corresponding to this small nucleation magnetic field Hn is present. By confirming that it appears in the hysteresis curve, it can be determined that the bottom surface 20 </ b> A of the recess 20 is located in an intermediate region in the thickness direction of the soft magnetic layer 14.

  The method of obtaining the nucleation magnetic field Hn is not limited to the method of obtaining from the hysteresis curve, and can be obtained, for example, by calculating numerical data obtained by measuring the magnetic Kerr effect characteristic.

  In this embodiment, the depth of the concave portion 20 of the concave / convex pattern of the magnetic recording medium 10 which is a finished product is inspected, but the concave portion depth of the concave / convex pattern of the intermediate product in the manufacturing process of the magnetic recording medium 10 is inspected. May be.

  In the magnetic recording medium 10, for example, the recording layer 16 is processed into a concavo-convex pattern by dry etching or the like, a filler 22 is formed, the concave portion 20 is filled with the filler 22, and the excess filler 22 is dry etched or the like. It is manufactured by removing and flattening, forming a protective layer 24, and applying a lubricating layer. For example, after processing the recording layer 16 into a concavo-convex pattern by dry etching or the like, and before forming the filler 22, the concave depth of the concavo-convex pattern of the intermediate product is inspected, and the recording layer 16 is not divided. If the intermediate product in which the bottom surface 20A of the recess 20 is not located in the region of the intermediate magnetic layer 18 is removed from the production line, the filler 22 is formed on the inappropriate intermediate product in which the recording layer 16 is not divided. This eliminates the need for post-processing and contributes to improved production efficiency.

  In the present embodiment, the filler 22, the protective layer 24, and the lubricating layer 26 are translucent, but in the case of inspecting the recess depth of the uneven pattern of the intermediate product in the manufacturing process of the magnetic recording medium 10. For the filler 22, the protective layer 24, and the lubricating layer 26, a material that does not have translucency or a material that has insufficient translucency may be used.

  In the present embodiment, the protective layer 24 is in direct contact with the recording element 16A and the filler 22, but a diaphragm having a low etching rate in the planarization step may be formed on the recording element 16A. The diaphragm may also be formed on the side surface of the recording element 16A and the bottom surface 20A of the recess 20. In the case of inspecting the depth of the concave portion of the concave / convex pattern of the finished magnetic recording medium, a translucent material is used as the material of the diaphragm. On the other hand, when inspecting the recess depth of the concave / convex pattern of the intermediate product in the manufacturing process of the magnetic recording medium 10, the filler 22, the material having no translucency as the material of the diaphragm, or the translucency is insufficient. Any material may be used.

  Further, in this embodiment, the protective layer 24 and the lubricating layer 26 are formed on the recording element 16A and the filler 22, but one or both of the protective layer 24 and the lubricating layer 26 are provided depending on the required performance. It may be omitted.

  In this embodiment, the recess 20 is formed partway in the thickness direction of the intermediate magnetic layer 18 and the entire bottom surface 20A exists in the region of the intermediate magnetic layer 18, but the bottom surface 20A of the recess 20 is the intermediate magnetic layer. A configuration matching the upper surface of the layer 18 may be employed.

  Also in this case, since the recording elements 16A of the recording layer 16 are divided, good recording / reproducing characteristics can be obtained. Further, since the magnetic Kerr effect characteristic is different from the case where the bottom surface 20A of the concave portion 20 of the concave / convex pattern is located in the middle region in the thickness direction of the recording layer 16, the concave portion depth of the concave / convex pattern of the recording layer 16 is reduced. It can be confirmed by destruction.

  In the present embodiment, the intermediate magnetic layer 18 has a single layer structure, but the intermediate magnetic layer has a plurality of layers in which the nucleation magnetic field in the thickness direction is different from the nucleation magnetic field in the thickness direction of the recording layer. It is good also as a structure.

  In the present embodiment, the underlayer 28 is formed between the intermediate magnetic layer 18 and the soft magnetic layer 14, but the underlayer may be omitted. The intermediate magnetic layer 18 may also serve as the underlayer.

  In this embodiment, the intermediate magnetic layer 18 is in direct contact with the recording layer 16, but another nonmagnetic layer may be formed between the intermediate magnetic layer 18 and the recording layer 16. Also in this case, the bottom surface 20A of the concave portion 20 of the concave / convex pattern is located in the region of the intermediate magnetic layer 18, and the bottom surface 20A of the concave portion 20 is located in the region of the recording layer 16 or other nonmagnetic layer. Thus, since the magnetic Kerr effect characteristic is different, the depth of the concave portion of the concave / convex pattern of the recording layer 16 can be confirmed nondestructively.

  In this embodiment, the underlayer 28 is formed between the intermediate magnetic layer 18 and the soft magnetic layer 16, but the nonmagnetic layer is interposed between the intermediate magnetic layer 18 and the soft magnetic layer 16. Other layers may be formed.

  In this embodiment, the soft magnetic layer 16 is in direct contact with the substrate 12, but an antiferromagnetic layer or an underlayer may be formed between the soft magnetic layer 16 and the substrate 12.

  In this embodiment, the nucleation magnetic field Hn in the thickness direction of the intermediate magnetic layer 18 is smaller than the nucleation magnetic field Hn in the thickness direction of the recording layer 16, but the nucleation magnetic field in the thickness direction of the intermediate magnetic layer 18. A configuration in which Hn is larger than the nucleation magnetic field Hn in the thickness direction of the recording layer 16 may be adopted. Also in this case, the position of the bottom surface 20A of the recess 20 can be confirmed by the difference between the nucleation magnetic fields Hn in the thickness direction of both.

  In the present embodiment, the magnetic recording medium 10 has the recording layer 16 or the like formed on one side of the substrate 12, but the present invention also applies to a double-sided recording type magnetic recording medium in which the recording layer or the like is formed on both sides of the substrate. The invention is applicable.

  In this embodiment, the magnetic recording medium 10 is a discrete track medium. However, the present invention is applicable to, for example, a patterned medium or a magnetic disk having a spiral track. The present invention is also applicable to magneto-optical disks and heat-assisted magnetic disks that use both magnetism and heat.

  The magnetic recording medium 10 having the same configuration as that of the above embodiment was inspected for the depth of the concave portion 20 of the concave / convex pattern of the recording layer 16 using the magnetic Kerr effect. The mask layer on the recording element 16A was completely removed. The main configuration of the manufactured magnetic recording medium 10 was as follows.

  The substrate 12 had a diameter of about 45 mm and the material was glass. The soft magnetic layer 14 had a thickness of about 100 nm, a material of FeCo alloy, a nucleation magnetic field Hn in the thickness direction of 0.06 kA / m, and a saturation magnetic flux density Bs of 1.5T. The recording layer 16 was about 12 nm in thickness, made of a CoCrPt alloy, a nucleation magnetic field Hn in the thickness direction of 270 kA / m, and a saturation magnetic flux density Bs of 0.5 T. The intermediate magnetic layer 18 had a thickness of about 18 nm, the material was a CoCrPt alloy having a composition different from that of the recording layer, the nucleation magnetic field Hn in the thickness direction was 59 kA / m, and the saturation magnetic flux density Bs was 0.12T. Ru (nonmagnetic material) was formed between the intermediate magnetic layer 18 and the soft magnetic layer 14 to a thickness of about 30 nm.

  The track pitch in the data area (the pitch in the radial direction between the recording elements 16A) was about 170 nm, and the width of the upper surface of the recording element 16A (the width in the radial direction) was about 85 nm. The depth of the recess 20 was 18 nm. That is, the concave portion 20 of the concave / convex pattern of the recording layer 16 is formed partway along the thickness direction of the intermediate magnetic layer 18, and the entire bottom surface 20 </ b> A of the concave portion 20 is located in the middle portion along the thickness direction of the intermediate magnetic layer 18. It was. The thickness of the portion under the bottom surface 20A of the recess 20 in the intermediate magnetic layer 18 was about 12 nm.

  In the magnetic Kerr effect characteristic measurement step (S102), conditions were set as follows.

Wavelength of light: 408nm
Light spot diameter: 2mm

  As a result, a hysteresis curve showing the relationship between the magnitude of the external magnetic field H and the Kerr rotation angle θk of the reflected light as shown in FIG. 5 was obtained.

[Comparative example]
In contrast to the above embodiment, the magnetic Kerr effect is applied to the magnetic recording medium 40 in which the bottom surface 20A of the recess 20 as shown in FIG. 14 is located in the middle of the recording layer 16 in the thickness direction. A characteristic measurement step (S102) was performed. The depth of the recess 20 was 6 nm. Other conditions were the same as those in the example.

  As a result, a hysteresis curve showing the relationship between the magnitude of the external magnetic field H and the Kerr rotation angle θk of the reflected light as shown in FIG. 13 was obtained.

  In the example, as shown in FIG. 5, a step S was present in the hysteresis curve. On the other hand, as shown in FIG. 13, in the comparative example, there was no step on the hysteresis curve. Therefore, it was confirmed that it is possible to determine whether or not the bottom surface 20A of the recess 20 is located in the region of the intermediate magnetic layer 18 based on the presence or absence of the step portion of the hysteresis curve.

[Simulation Example 1]
Two types of simulation models under the same conditions as in the above-described examples and comparative examples and four types of simulation models in which the depths of the recesses 20 are different from these were prepared. Specifically, six types of simulation models in which the depth of the recess 20 is 0, 6, 12, 18, 24, and 30 nm were produced.

  The magnetic gap (gap between the upper surface of the recording element 16A and the lower surface of the magnetic head) was set to 18 nm. The linear recording density was set to 970 kbpi. Other conditions were set to the same conditions as in the above examples and comparative examples. Incidentally, the saturation magnetic flux density Bs of the recording layer 16 was set to 0.5.

  The recording / reproduction simulation was executed under the above conditions, and the S / N ratio of each simulation model was calculated. The relationship between the depth of the recess 20 and the S / N ratio is shown in Table 1 and FIG.

  Also, for these six types of simulation models, six types of simulation models are prepared in which the saturation magnetic flux density Bs of the recording layer 16 is set to 1.0, the simulation is executed, and the S / N ratio of each simulation model is calculated. did. Table 1 shows the relationship between the depth of the recess 20 and the S / N ratio.

  Furthermore, for the above six types of simulation models, six types of simulation models are prepared in which the saturation magnetic flux density Bs of the recording layer 16 is set to 0.3, the simulation is executed, and the S / N ratio of each simulation model is calculated. did. Table 1 shows the relationship between the depth of the recess 20 and the S / N ratio.

  As shown in Table 1 and FIG. 10, when the depth of the recess 20 is shallower than 12 nm and the bottom surface 20A of the recess 20 is located in the region of the recording layer 16, the S / N ratio is relatively low, and The S / N ratio tended to decrease as the depth of the recess 20 was shallower. On the other hand, when the depth of the recess 20 is 12 nm or more and less than 30 nm and the bottom surface 20A of the recess 20 is located in the region of the intermediate magnetic layer 18, the S / N ratio is constant, and the S / N ratio is The depth was 30 nm, which was the same high value as when the intermediate magnetic layer 18 was divided.

  That is, even when the non-divided intermediate magnetic layer 18 is disposed under the recording layer 16, the intermediate magnetic layer 18 is divided if the bottom surface 20 </ b> A of the recess 20 is positioned in the region of the intermediate magnetic layer 18. It was confirmed that the same good S / N ratio was obtained.

[Simulation example 2]
In contrast to the above embodiment, the depth of the recess 20 is 12 nm, the bottom surface 20A of the recess 20 coincides with the upper surface of the intermediate magnetic layer 18, the saturation magnetic flux density Bs of the recording layer is 1.0 T, and the saturation of the intermediate magnetic layer 18 Six types of simulation models having magnetic flux densities Bs of 0.0, 0.05, 0.1, 0.15, 0.2, and 0.3T were produced.

  As in the simulation example 1, the magnetic gap (gap between the upper surface of the recording element 16A and the lower surface of the magnetic head) was set to 18 nm. The linear recording density was set to 970 kbpi. Other conditions were set to be the same as in the above example.

  The simulation was executed under the above conditions, and the S / N ratio of each simulation model was calculated. FIG. 11 shows the relationship between the saturation magnetic flux density Bs of the intermediate magnetic layer 18 and the S / N ratio.

  Also, for these six types of simulation models, six types of simulation models were prepared in which the saturation magnetic flux density Bs of the recording layer was set to 0.3 T, the simulation was executed, and the S / N ratio of each simulation model was calculated. . FIG. 12 shows the relationship between the saturation magnetic flux density Bs of the intermediate magnetic layer 18 and the S / N ratio.

  As shown in FIG. 11 and FIG. 12, the saturation magnetic flux density Bs of the intermediate magnetic layer 18 in both cases where the saturation magnetic flux density Bs of the recording layer is set to 1.0T and 0.3T. Is larger than 0.15T, the S / N ratio is relatively low, and the S / N ratio tends to decrease as the saturation magnetic flux density Bs of the intermediate magnetic layer 18 increases. On the other hand, when the saturation magnetic flux density Bs of the intermediate magnetic layer 18 is 0.15 T or less, the S / N ratio is constant and the same as when the saturation magnetic flux density Bs of the intermediate magnetic layer 18 is zero. It was a high value.

  That is, even if the non-divided intermediate magnetic layer 18 is disposed under the recording layer 16, it is the same as when no intermediate magnetic layer exists if the saturation magnetic flux density Bs of the intermediate magnetic layer 18 is 0.15 T or less. It was confirmed that a good S / N ratio was obtained.

  If the saturation magnetic flux density Bs of the intermediate magnetic layer 18 is smaller than 0.05T, it becomes difficult to discriminate the nucleation magnetic field Hn of the intermediate magnetic layer 18 and the recording layer 16 in the hysteresis curve, and the steps of the hysteresis curve corresponding to these Since it becomes difficult to discriminate the bent portion, the saturation magnetic flux density Bs of the intermediate magnetic layer 18 is preferably 0.05T or more.

  The present invention can be used for a magnetic recording medium in which a recording layer is divided into a large number of recording elements in a predetermined uneven pattern, such as a discrete track medium and a patterned medium.

1 is a perspective view schematically showing a schematic structure of a magnetic recording / reproducing apparatus according to an embodiment of the present invention. Sectional drawing along the radial direction which shows typically the structure of the magnetic recording medium of the magnetic recording / reproducing apparatus Flowchart showing an outline of a method for inspecting the recess depth of the uneven pattern of the magnetic recording medium Block diagram showing the outline of the configuration of the car rotation angle measuring device used for the inspection Hysteresis curve showing the relationship between the magnitude of the external magnetic field H applied to the magnetic recording medium according to the embodiment of the present invention and the Kerr rotation angle θk A graph schematically showing an enlarged part of FIG. The graph which expands and schematically shows some other examples of the hysteresis curve concerning the embodiment of the present invention. The graph which expands and schematically shows some other examples of the hysteresis curve concerning the embodiment of the present invention. The graph which expands and schematically shows some other examples of the hysteresis curve concerning the embodiment of the present invention. The graph which shows the relationship between the depth of the recessed part which concerns on the simulation example 1, and S / N ratio The graph which shows the relationship between the saturation magnetic flux density Bs and S / N ratio of the intermediate | middle magnetic layer which concerns on the simulation example 2 The graph which shows the relationship between the saturation magnetic flux density Bs and S / N ratio of the intermediate | middle magnetic layer which were calculated by the other simulation which concerns on the simulation example 2. Hysteresis curve showing the relationship between the magnitude of the external magnetic field H applied to the magnetic recording medium according to the comparative example and the Kerr rotation angle θk Sectional drawing which follows the radial direction which shows the structure of the magnetic recording medium which concerns on a comparative example typically

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetic recording / reproducing apparatus 10 ... Magnetic recording medium (inspection object)
DESCRIPTION OF SYMBOLS 12 ... Substrate 14 ... Soft magnetic layer 16 ... Recording layer 16A ... Recording element 18 ... Intermediate magnetic layer 20 ... Recess 22 ... Filler 24 ... Protective layer 26 ... Lubricating layer 28 ... Underlayer S ... Step part S102 ... Magnetic Kerr effect characteristic Measurement step S104 ... Depression depth discrimination step

Claims (10)

A substrate, a soft magnetic layer formed on the substrate, a recording layer formed on the soft magnetic layer and divided into a plurality of recording elements in a predetermined uneven pattern, and a nucleus in the thickness direction An intermediate magnetic layer formed between the recording layer and the soft magnetic layer, the magnitude of the forming magnetic field being different from the magnitude of the nucleation magnetic field in the thickness direction of the recording layer, and a saturation magnetic flux of the intermediate magnetic layer The density is smaller than the saturation magnetic flux density of the recording layer, the saturation magnetic flux density of the intermediate magnetic layer is in the range of 0.05 to 0.15 T, and the bottom surface of the concave portion of the concave / convex pattern is the region of the intermediate magnetic layer A magnetic recording medium characterized by being located in In claim 1,
A magnetic recording medium wherein the nucleation magnetic field in the thickness direction of the intermediate magnetic layer is smaller than the nucleation magnetic field in the thickness direction of the recording layer. In claim 1 or 2 ,
A magnetic recording medium further comprising a translucent filler filled in the concave portions of the concave / convex pattern. In claim 3 ,
A magnetic recording medium further comprising a translucent protective layer covering the upper surface of the recording element and the upper surface of the filler. Magnetic recording and reproducing apparatus characterized by having a magnetic recording medium according to any one of claims 1 to 4. A substrate, a soft magnetic layer formed on the substrate, a recording layer formed on the soft magnetic layer and divided into a plurality of recording elements in a predetermined uneven pattern, and a nucleation magnetic field in the thickness direction Unlike the magnitude of the nucleation magnetic field in the thickness direction of the recording layer, the light is applied to the surface on the recording layer side of the object to be inspected including the intermediate magnetic layer formed between the recording layer and the soft magnetic layer. A magnetic Kerr effect characteristic measuring step for measuring the magnetic Kerr effect characteristic by irradiating and measuring the reflected light, and the bottom surface of the concave portion of the concave and convex pattern is a region of the intermediate magnetic layer based on the measurement result of the magnetic Kerr effect characteristic And a recess depth determining step for determining whether or not the recess is located on the recess pattern. In claim 6 ,
In the recess depth determining step, the bottom surface of the recess of the concavo-convex pattern is any of the recording layer region, the intermediate magnetic layer region, and the soft magnetic layer region based on the measurement result of the magnetic Kerr effect characteristic. It is discriminate | determined whether it is located in the recessed part depth inspection method of the uneven | corrugated pattern characterized by the above-mentioned. In claim 6 or 7 ,
In the magnetic Kerr effect characteristic measurement step, an external magnetic field is applied to the object to be inspected while varying the magnitude thereof, and the Kerr rotation angle is measured as the magnetic Kerr effect characteristic. In the recess depth determination step, the external magnetic field is measured. A concave / convex pattern concave portion depth inspection method, comprising: determining a position of a bottom surface of a concave portion of the concave / convex pattern based on a hysteresis curve indicating a relationship between a size and the Kerr rotation angle. In claim 8 ,
In the step of determining the depth of the recess, it is determined whether or not the bottom surface of the recess is located in the region of the intermediate magnetic layer based on the presence or absence of a step portion of the hysteresis curve. Inspection method. In any one of Claims 6 thru | or 9 .
A concave / convex pattern concave portion depth inspection method, comprising: determining a position of a bottom surface of the concave portion based on a magnitude of a nucleation magnetic field obtained by measuring the magnetic Kerr effect characteristic.

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