CN102779533B - FeRhPt laminated film that a kind of phase transition temperature is adjustable and preparation method thereof - Google Patents

Abstract

The invention relates to the field of magnetic materials, and specifically discloses a FeRhPt composite thin film with adjustable phase transition temperature and a preparation method thereof. The FeRhPt composite thin film with adjustable phase transition temperature of the present invention includes a single crystal MgO substrate and (FeRh ) _100-X Pt _X alloy film, where the range of x is 0<x<20. The present invention realizes the epitaxial growth and vertical orientation of the FeRhPt film by using a single crystal MgO (001) substrate, and obtains a relatively perfect CsCl ordered structure; and induces the ordering of the FeRhPt composite film through annealing treatment, so that the material has anti-iron Magnetic/ferromagnetic phase transition, and a series of FeRhPt composite thin films with adjustable phase transition temperature were prepared. The invention has the advantages of simple preparation method, good material performance and the like, and is suitable for the preparation of FeRhPt composite film with adjustable phase transition temperature.

Description

A kind of FeRhPt composite film with adjustable phase transition temperature and preparation method thereof

technical field

The invention relates to the field of magnetic materials, and specifically discloses an FeRhPt composite thin film with adjustable phase transition temperature and a preparation method thereof.

Background technique

Existing studies have found that in a lower temperature range (330K ~ 350K) FeRh alloy has a first-order phase transition from antiferromagnetic to ferromagnetic. This phase transition is considered to be related to the CsCl-type body-centered cubic structure of the Fe50Rh50 alloy.

Fallot discovered for the first time in 1938 that ordered FeRh-based alloys with a CsCl structure had a first-order antiferromagnetic/ferromagnetic phase transition. Heating from room temperature to the phase transition temperature (about 350K), the ordered FeRh alloy undergoes a magnetic phase transition from AFM to FM, with a magnetic hysteresis of about 10K (J.LommelandJ.Kouvel, J.Appl.Phys ., Vol.38, pp1263～1264, 1967). Further research found that the phase transition process is accompanied by a 1%-2% unit cell volume expansion, a decrease in resistivity, and a large entropy change. In addition, it is also studied in J.Appl.Phys., Vol.74, pp3328, 1993; J.Appl.Phys., Vol.90, pp6251, 2001 and IEEETran.Magn., vol.40, pp2537, 2004 and other documents Phase transformation of FeRh alloy. Taking advantage of the antiferromagnetic/ferromagnetic first-order phase transition behavior of FeRh ordered alloys, J. Thiele et al. (IEEETran.Magn., vol.40, pp2537, 2004) developed a FeRh/FePt bilayer for heat-assisted magnetic recording Thin films; Zhou et al. (US Patent US20090052092A1) developed a perpendicular magnetic recording head containing a FeRh layer; E.Fullerton et al. (US Patent US007372116B2) developed a magnetic random memory cell with thermally assisted flipping.

Normally, the temperature of antiferromagnetic/ferromagnetic phase transition of ordered FeRh alloy with CsCl structure is around 350K. However, its phase transition temperature is sensitive to the composition of the sample and can be adjusted by doping. Adding a small amount of Ir or Pt can increase the phase transition temperature and adding a small amount of Pd can lower the phase transition temperature. By adjusting the antiferromagnetic/ferromagnetic phase transition temperature of the FeRh-based alloy, the alloy can be used in a wider range of technologies, such as heat-assisted magnetic recording media, spin valves, magnetic refrigeration and micro-nano electromechanical system etc.

Contents of the invention

The purpose of the present invention is to overcome the defects of the prior art, by adding different amounts of Pt in the FeRh alloy film to adjust the antiferromagnetic/ferromagnetic phase transition temperature of the alloy film, to provide a FeRhPt composite film with adjustable phase transition temperature And its preparation method makes it meet the technical application in a wider range.

The first aspect of the present invention discloses a FeRhPt composite thin film with adjustable phase transition temperature, including a single crystal MgO (001) substrate and a (FeRh) _100-X Pt _X alloy thin film on it, and the value range of x is 0 <x<20.

Preferably, the thickness of the (FeRh) _100-X Pt _X alloy thin film is 5-100 nm.

The second aspect of the present invention discloses the preparation method of the aforementioned FeRhPt composite film with adjustable phase transition temperature, the steps are:

1) Deposition of thin film: Deposit (FeRh) _100-X Pt _X alloy thin film on single crystal (001) MgO substrate by deposition method, where the value range of x is 0<x<20;

2) Annealing treatment: After the substrate is naturally cooled, the deposited thin film is annealed in vacuum to obtain a FeRhPt composite thin film.

Preferably, the deposition method is physical vapor deposition.

More preferably, the deposition method is magnetron sputtering deposition method.

The magnetron sputtering deposition method is as follows: a co-sputtering method of Fe ₅₀ Rh ₅₀ alloy target and Pt target is used, and the sputtering is carried out in an argon atmosphere.

^Optimally , the conditions of the magnetron sputtering deposition method are: the temperature of the substrate during sputtering is ^100-500 °C; Air pressure 1 ~ 20Pa.

Optimally, during the sputtering process of the magnetron sputtering deposition method, the substrate rotates at a rate of 5 rpm to 30 rpm.

Preferably, the conditions of the annealing treatment are: a vacuum degree of 1×10 ^-5 to 10×10 ^-5 Pa, an annealing temperature of 400-700° C., and an annealing time of 0.5-4 hours.

The third aspect of the present invention discloses the application of the aforementioned FeRhPt composite film with adjustable phase transition temperature as a magnetic recording medium.

The present invention uses single crystal MgO (001) as the substrate, mainly to realize the epitaxial growth and vertical orientation of the FeRhPt thin film, and to obtain a relatively perfect CsCl ordered structure; in addition, the preparation method of the present invention is also induced by annealing to complete the FeRhPt composite thin film Ordered, with antiferromagnetic/ferromagnetic phase transition, and finally a series of FeRhPt composite thin films with adjustable antiferromagnetic/ferromagnetic phase transition temperature, which makes the alloy have the possibility of wider technical application. The preparation method of the present invention is simple, the prepared material has good performance, and is very suitable for the preparation of FeRhPt composite film with adjustable phase transition temperature.

Description of drawings

Figure 1: The relationship between magnetization and temperature of FeRhPt composite thin film

Figure 2: X-ray Diffraction Pattern

detailed description

The present invention will be further described below in conjunction with specific examples. It should be understood that the examples are only used to illustrate the present invention and are not intended to limit the protection scope of the present invention.

Example 1

1. Experimental method

1) Firstly, the single crystal MgO (001) substrate was cleaned in an alcohol solution with an ultrasonic cleaning device, and dried with compressed air. The cleaned and dried MgO substrate was placed on the sample base of the sputtering chamber with tweezers.

2) When the vacuum at the back of the sputtering chamber reaches 2×10 ^-5 Pa, use radio frequency magnetron sputtering technology to pass co-sputtering technology on a clean MgO substrate, using Fe ₅₀ Rh ₅₀ alloy target and Pt target co-sputtering The deposition method is to deposit (FeRh) ₉₅ Pt ₅ alloy film (the value in the chemical formula is the molar ratio), and its thickness is 50nm. During sputtering, the substrate temperature was 100°C. Argon gas pressure was 10 Pa during sputtering. During sputtering, the substrate was rotated at a rate of 12 rpm.

3) After sputtering, the substrate is naturally cooled to room temperature, and then placed in a vacuum annealing furnace for annealing heat treatment. The background vacuum degree of the vacuum annealing furnace is 10×10 ^-5 Pa, the annealing temperature is 700° C., and the annealing time is 0.5 hour.

2. Experimental results

After testing, the antiferromagnetic/ferromagnetic phase transition temperature of the prepared thin film is about 450K, and the Curie temperature is about 650K. The relationship between magnetization and temperature of (FeRh) ₉₅ Pt ₅ composite thin film is shown in Figure 1.

Example 2

1. Experimental method

1) First, the single crystal MgO (001) substrate was cleaned in an alcohol solution using an ultrasonic cleaning device, and dried with compressed air. Place the cleaned and dried MgO substrate on the sample base of the sputtering chamber with tweezers.

2) When the vacuum at the back of the sputtering chamber reaches 0.7×10 ^-5 Pa, use radio frequency magnetron sputtering technology to pass co-sputtering technology on a clean MgO substrate, using Fe ₅₀ Rh ₅₀ alloy target and Pt target co-sputtering By means of radiation, deposit (FeRh) ₉₀ Pt ₁₀ alloy film (the value in the chemical formula is the molar ratio), and its thickness is 100nm. During sputtering, the substrate temperature was 350°C. Argon gas pressure was 20 Pa during sputtering. During sputtering, the substrate was rotated at a rate of 5 rpm.

3) After sputtering, the substrate is naturally cooled to room temperature, and then placed in a vacuum annealing furnace for annealing heat treatment. The background vacuum degree of the vacuum annealing furnace is 5×10 ^-5 Pa, the annealing temperature is 500° C., and the annealing time is 2 hours.

2. Experimental results

After detection, the antiferromagnetic/ferromagnetic phase transition temperature of the prepared thin film is about 490K, and the Curie temperature is about 600K. The relationship between magnetization and temperature is shown in Figure 1.

Example 3

1. Experimental method

1) First, the single crystal MgO (001) substrate was cleaned in an alcohol solution using an ultrasonic cleaning device, and dried with compressed air. Place the cleaned and dried MgO substrate on the sample base of the sputtering chamber with tweezers.

2) When the vacuum at the back of the sputtering chamber reaches 5×10 ^-5 Pa, use radio frequency magnetron sputtering technology to pass co-sputtering technology on a clean MgO substrate, using Fe ₅₀ Rh ₅₀ alloy target and Pt target co-sputtering By means of radiation, deposit (FeRh) ₈₅ Pt ₁₅ alloy film (the value in the chemical formula is the molar ratio), and its thickness is 5nm. During sputtering, the substrate temperature was 500°C. Argon gas pressure was 1.0 Pa during sputtering. During sputtering, the substrate was rotated at a rate of 30 rpm.

3) After sputtering, the substrate is naturally cooled to room temperature, and then placed in a vacuum annealing furnace for annealing heat treatment. The background vacuum degree of the vacuum annealing furnace is 1×10 ^-5 Pa, the annealing temperature is 400° C., and the annealing time is 4 hours.

2. Experimental results

After testing, the antiferromagnetic/ferromagnetic phase transition of the prepared thin film is about 520K, and the Curie temperature is about 570K. The relationship between magnetization and temperature is shown in Figure 1.

As can be seen from the relationship curves between the magnetization and temperature of the materials in Examples 1-3, the prepared FeRhPt films all have antiferromagnetic/ferromagnetic phase transitions; the phase transition temperature increases with the increase of the Pt content, ranking first The Li temperature decreases with the increase of Pt content, and the thermal hysteresis width accompanying the phase transition decreases with the increase of Pt content.

The X-ray diffraction shown in Figure 2 shows that the film has a vertically oriented CsCl type body-centered cubic structure, indicating that the FeRhPt film is prepared by magnetron sputtering, and then after subsequent heat treatment can obtain a CsCl ordered structure, vertical orientation and phase transition. The FeRhPt thin film with adjustable temperature is suitable for applications such as heat-assisted magnetic recording media, spin valves, magnetic refrigeration, and micro-nano electromechanical systems in the future.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any form and in essence. Several improvements and supplements can be made, and these improvements and supplements should also be regarded as the protection scope of the present invention. Those who are familiar with this profession, without departing from the spirit and scope of the present invention, when they can use the technical content disclosed above to make some changes, modifications and equivalent changes of evolution, are all included in the present invention. Equivalent embodiments; at the same time, all changes, modifications and evolutions of any equivalent changes made to the above-mentioned embodiments according to the substantive technology of the present invention still belong to the scope of the technical solution of the present invention.

Claims (6)

1. the FeRhPt laminated film that phase transition temperature is adjustable, comprises monocrystalline MgO (001) substrate and (FeRh) on it _100-Xpt _xalloy firm, and the span of x is 10<x<15; The FeRhPt laminated film that described phase transition temperature is adjustable is that the method by comprising the following steps prepares:

1) deposition of film: deposit (FeRh) by sedimentation on monocrystalline MgO (001) substrate _100-Xpt _xalloy firm, wherein the span of x is 10<x<15;

2) annealing in process: after substrate cools naturally, the film obtained deposition in a vacuum carries out annealing in process and obtains FeRhPt laminated film;

Described sedimentation is magnetron sputtering deposition method;

The condition of described magnetron sputtering deposition method is: sputtering time substrate temperature 100 ~ 500 DEG C; The back end vacuum tightness 0.7 × 10 of sputtering chamber ^-5~ 5 × 10 ^-5pa, ar pressure 1 ~ 20Pa during sputtering;

In magnetron sputtering deposition method sputter procedure, substrate rotates with the speed of 5 revs/min ~ 30 revs/min;

Step 2) condition of described annealing in process is: vacuum tightness 1 × 10 ^-5~ 10 × 10 ^-5pa, annealing temperature 400 ~ 700 DEG C, annealing time 0.5 ~ 4 hour;

Described (FeRh) _100-Xpt _xalloy firm thickness is 5 ~ 100nm; Described FeRhPt laminated film has the body-centered cubic structure of vertical orientated CsCl type.

2. the preparation method of FeRhPt laminated film according to claim 1, step is:

1) deposition of film: deposit (FeRh) by sedimentation on monocrystalline MgO (001) substrate _100-Xpt _xalloy firm, wherein the span of x is 10<x<15;

2) annealing in process: after substrate cools naturally, the film obtained deposition in a vacuum carries out annealing in process and obtains FeRhPt laminated film;

Step 1) described sedimentation is magnetron sputtering deposition method.

3. preparation method as claimed in claim 2, it is characterized in that, the condition of described magnetron sputtering deposition method is: sputtering time substrate temperature 100 ~ 500 DEG C; The back end vacuum tightness 0.7 × 10 of sputtering chamber ^-5~ 5 × 10 ^-5pa, ar pressure 1 ~ 20Pa during sputtering.

4. preparation method as claimed in claim 2, it is characterized in that, in magnetron sputtering deposition method sputter procedure, substrate rotates with the speed of 5 revs/min ~ 30 revs/min.

5. preparation method as claimed in claim 2, is characterized in that, step 2) condition of described annealing in process is: vacuum tightness 1 × 10 ^-5~ 10 × 10 ^-5pa, annealing temperature 400 ~ 700 DEG C, annealing time 0.5 ~ 4 hour.

6. FeRhPt laminated film according to claim 1 is as the application of magnetic recording media.