JP2763920B2 - Bloch line memory device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a Bloch line device using a vertical Bloch line pair as a storage information unit and useful for an external memory for a computer, a memory for a file device, etc. Regarding stabilization of line pairs.

(Prior art)

With the rise of high-density storage elements, IEEE Trans.Magn.MA
The Bloch line memory device disclosed in G 19, 1838 (1983), Japanese Patent Application Laid-Open No. 59-11092, etc. has attracted attention in recent years because of its enormous storage capacity and non-volatility.

The Bloch line memory device consists of an information storage unit consisting of a domain wall around a stripe domain in which a bubble domain is elongated, and stores information in the presence or absence of a vertical Bloch line pair. Indicates that a Bloch line pair exists regularly as a storage information unit. For example, when a Bloch line pair exists, it corresponds to “1”, and when there is no Bloch line pair, it corresponds to “0”.
The Bloch line pair is sequentially transferred to an adjacent potential well by applying a vertical pulse magnetic field at the time of writing or reading.

The main components of such a Bloch line memory device are (YSmLuCa) ₃ (FeGe) ₅ O ₁₂ , (YSmTm) by epitaxial growth on a substrate 1 generally made of a rare earth garnet single crystal such as GGG as shown in FIG. ₃ (FeG
e) A magnetic garnet film 2 made of ₅ O ₁₂ or the like is provided, and GdCo, T
A perpendicular magnetic film 3 made of a rare earth metal-transition metal based amorphous alloy film such as bFe, GdFe, GdFeCo, TbFeCo or a polycrystalline film such as CoPt or CoCr is provided. If necessary, an insulating film such as Si ₃ N ₄ or SiO ₂ SiO is provided between the magnetic film 2 and the perpendicular magnetic film 3. Although not shown, the perpendicular magnetization film 3 is so arranged that the stripe domains are regularly arranged in parallel.
Are patterned in parallel and regularly, and a conductor for writing / reading is provided in the direction perpendicular to the perpendicular magnetization film via an insulating film. The entire device has been applied bias field H _B, the stripe domain 4 is stabilized around a perpendicular magnetization film which is saturated in the direction opposite to the bias magnetic field H _B. Instead of the perpendicular magnetization film pattern, a soft magnetic film pattern such as permalloy may be used. The stripe domain is stabilized by the leakage magnetic field from both the perpendicular magnetization film pattern and the soft magnetic film pattern.

Other methods of stabilizing the stripe domain include a method of providing a groove in the valve magnetic film and stabilizing it by a demagnetizing field generated near a step portion of the groove, and providing a loop-shaped conductor on the bubble magnetic film. There is a method of stabilizing by generating a vertical magnetic field in a loop area by flowing a current through a conductor. FIG. 2 shows an example in which a groove is provided in the magnetic film. This groove (a groove reaching the substrate) may be at a predetermined position (position where the stripe domain is stabilized) with a width of about 1/2 of the magnetic domain (domain) width. provided, the stripe domain 4 is stabilized around the groove by applying a bias magnetic field H _B.

However, in the stripe domain stabilization method as described above, a pattern is formed on the magnetic film for bubbles or the magnetic film itself is processed, so if a conductor or the like is further provided thereon, a step occurs and the shape in the film thickness direction is generated. Therefore, a flattening process is required, and when a patterned film is provided on the magnetic film for bubbles, stress is generated between the magnetic film and the magnetic wall is caught, and depending on the case of the magnetic wall, There is a problem that the stability of the stripe domain is different, and that a stable vertical Bloch line cannot be transferred.

[Problems to be solved by the invention]

An object of the present invention is to solve the above-described problems in the prior art and eliminate the need for a flattening process to avoid unevenness in the potential well of the domain wall due to the stress of the magnetic film and the shape of the groove, etc. It is an object of the present invention to provide a Bloch line memory device capable of accurate and reliable stabilization, and thus capable of stable transfer of Bloch line pairs.

[Configuration and operation of the invention]

The Bloch line memory device of the present invention is a Bloch line memory device having a magnetic film exhibiting perpendicular magnetic anisotropy that stores a vertical Bloch line pair as a storage information unit on a domain wall of a stripe domain. The stripe domain is stabilized in a region exhibiting perpendicular magnetic anisotropy by providing a region exhibiting magnetic anisotropy or paramagnetism other than the above. As described above, in the device of the present invention, the stripe domain is stabilized in the magnetic film for bubbles without using the conventional flattening process.

The Bloch line memory device of the present invention will be described with reference to the drawings. FIGS. 3 to 5 are sectional views showing main components of the device of the present invention. In FIGS. 3 and 4, the perpendicular magnetic anisotropy is shown. In the case of FIG. 3, the amorphous regions 2b exhibiting paramagnetism are provided in parallel in the single crystal magnetic garnet film 2 shown in FIG. 2a.),
In the case of FIG. 4, the stripe domain 4 is stabilized between two paramagnetic regions 2b. In the case of FIG. 5, a rare earth metal-transition metal based amorphous magnetic film exhibiting perpendicular magnetic anisotropy is shown. 2 is provided with a strip-shaped polycrystalline region 2b exhibiting magnetic anisotropy other than perpendicular (for example, in-plane) (hereinafter referred to as heteromagnetic anisotropy). Is stabilized.

There are generally two methods for producing the device of the present invention as described above. One is to coat a non-magnetic substrate surface such as a rare earth garnet single crystal such as GGG, quartz, glass, plastic, etc., with a photoresist except for a portion that is in charge of a region exhibiting paramagnetism or heteromagnetic anisotropy. After performing ion irradiation from the substrate, the photoresist is removed, and (YSmLuCa) ₃ (FeGe) ₅ O ₁₂ , (YSm
LuLu) ₃ (FeGe) ₅ O ₁₂ , (YSmTm) ₃ (FeGe) ₅ O _{12 and} other magnetic garnet materials are deposited by RF magnetron sputtering, LPE (liquid phase epitaxy), etc. .
This is a method for forming a magnetic garnet film having a thickness of about 1 to 5 μm. In this case, a film (region) of an amorphous structure showing paramagnetism is formed in an ion irradiated portion of the substrate, and a film of a single crystal structure showing a perpendicular magnetic anisotropy having a small coercive force Hc by epitaxial growth in a portion not receiving ion irradiation. (Region) is formed.

Another method uses GdCo, TbFe, Gd on the untreated substrate.
A rare earth metal-transition metal based amorphous alloy such as Fe, GdFeCo, TbFeCo, etc. is formed by a film forming method such as an RF magnetron sputtering method and has a perpendicular magnetic anisotropy of about 0.1 to 5 μm in thickness. In this method, after forming an alloy magnetic film, laser light is irradiated and annealed in a pattern from above on a region exhibiting anomalous magnetic anisotropy. In this case, the portion of the magnetic film irradiated with laser light has a polycrystalline structure, and a region showing in-plane magnetic anisotropy is formed, while the portion not irradiated with laser light has perpendicular magnetic anisotropy of an amorphous structure. The film (region) shown remains as it is.

Other than the above two methods, formation of a different magnetic anisotropy or paramagnetic region is possible. For example, it is possible to form a paramagnetic region or a different magnetic anisotropic region by implanting ions into the substrate surface, or to form a different magnetic anisotropic region by irradiating an amorphous perpendicular magnetization film with an ion beam or an electron beam.

In the device of the present invention, as shown in FIGS.
Via an insulating layer (made of Si ₃ N ₄ , SiO ₂ , SiO, etc.) (not shown) having a thickness of about 1 μm, a conductor 5 for generating a bubble, a conductor 6 for controlling a Bloch line, and chopping having a thickness of about 0.1 to 1 μm, respectively. Conductor 7 (Au, A
g, Al, Cu, etc.) are provided by patterning. 2b is a guide paramagnetic region.

 Hereinafter, a production example of the device of the present invention will be described.

Embodiment 1 This embodiment is an example in which a stripe domain is stabilized around a region 2b exhibiting paramagnetism as shown in FIG.

A photoresist is coated on a substrate made of Gd ₃ Ga ₅ O ₁₂ except for a portion corresponding to the region 2b showing paramagnetism as shown in FIG. 6, and ion irradiation is performed under the following conditions.

Gas pressure: Ar, 5 × 10 ^-3 Torr RF discharge power: 200 W, 13.56 MHz Irradiation time: 10 min Next, 100 m as a target on the substrate thus treated
(YSmTm) ₃ (FeGe) ₅ O ₁₂ of mφ was formed by RF magnetron sputtering under the following conditions to form a magnetic garnet film having a thickness of about 2 μm.

Residual gas pressure: 1 × 10 ⁻⁶ Torr Ar gas pressure: 5 × 10 ⁻³ Torr RF discharge power: 400 W Substrate temperature: 500 ° C. As a result, the garnet film formed on the part irradiated with substrate ions is amorphous The structure shows paramagnetism,
The portion of the film where the substrate was not irradiated with ions had a single crystal structure grown epitaxially and was a perpendicular magnetic anisotropic film having a small coercive force Hc.

A 0.5 μn thick Si ₃ N ₄ insulating layer is provided on the magnetic film near the tip of the stripe domain by a conventional method, and a 0.5 μm thick Au bubble generating conductor and a Bloch line are respectively controlled thereon. A Bloch line memory device of the present invention as shown in FIG. 6 was manufactured by providing a conductor for chopping and a conductor for chopping.
In this embodiment, the guide paramagnetic region 2b is provided at the end between the stripe domains 4 so as to extend straight when the stripe domain is extended.

Embodiment 2 In this embodiment, as shown in FIG. 4, a stripe domain is stabilized between two paramagnetic regions.

A photoresist is coated on a substrate made of Gd ₃ Ga ₅ O ₁₂ except for a portion corresponding to the region 2b showing paramagnetism as shown in FIG. 7, and ion irradiation is performed under the following conditions.

Gas pressure: Xe, 5 × 10 ^-3 Torr RF discharge power: 200 W, 13.56 MHz Irradiation time: 10 min Next, 10
(YSmLu) ₃ (FeGe) ₅ O ₁₂ having a diameter of 0 mm was formed by RF magnetron sputtering under the same conditions as in Example 1 to form a magnetic garnet film having a thickness of about 2 μm.

Hereinafter, an insulating layer made of Si ₃ N ₄ is provided on the magnetic film in the vicinity of the tip of the stripe domain in the same manner as in Example 1, and further thereon, a conductor for Au bubble generation, a conductor for Bloch line control, and The Bloch line memory device of the present invention was manufactured by providing a chopping conductor. In this example, as shown in FIG. 7, the stripe domain was surrounded by a paramagnetic region so as not to extend to one side (the right side in FIG. 7).

Embodiment 3 In this embodiment, as shown in FIG. 5, a stripe domain is stabilized between two different magnetic anisotropic regions.

Gd _0.2 Co of 100mmφ as a target on a glass substrate
_An alloy of _0.8 was formed under the following conditions by an RF magnetron sputtering method to prepare a rare earth metal-transition metal based amorphous magnetic film having a thickness of about 2 μm.

Residual gas pressure: 1 × 10 ⁻⁶ Torr Ar gas pressure: 5 × 10 ⁻³ Torr RF discharge power: 400 W Substrate temperature: water cooled Next, the magnetic film exhibits anomalous magnetic anisotropy as shown in FIG. 30mW Ar laser light (beam diameter:
(About 1.5 μm) and annealed (about 400 ° C.). As a result, the portion irradiated with the laser had a polycrystalline structure and exhibited in-plane magnetic anisotropy, and the portion not irradiated with the laser exhibited perpendicular magnetic anisotropy up to the amorphous structure.

Thereafter, an insulating layer made of Si ₃ N ₄ is provided on the magnetic film near the leading end of the stripe domain in the same manner as in Example 1, and a Au bubble-generating conductor, a Bloch line controlling conductor, and a chopping line are formed thereon. The Bloch line memory device of the present invention was manufactured by providing a conductor for use. In this example, as shown in FIG. 7, the stripe domain was surrounded by a different magnetic anisotropic region so as not to extend to one side (the right side in FIG. 7).

[Function and effect of the invention]

In the Bloch line memory device of the present invention, since a region exhibiting heteromagnetic anisotropy or paramagnetism is provided in a conventional magnetic film exhibiting perpendicular magnetic anisotropy, a domain wall portion due to stress of the magnetic film, the shape of the groove, etc. Accurate and reliable stabilization of the stripe domain, avoiding potential well non-uniformities, and thus stable transfer of Bloch line pairs is possible. Further, since the stripe domain can be stabilized without the need for a planarization process, an accurate pattern such as a conductor can be formed on the film, and highly reliable writing, reading and transfer can be performed.

[Brief description of the drawings]

1 and 2 are cross-sectional views of main components of a conventional Bloch line memory device, FIGS. 3 to 5 are cross-sectional views of main components of a Bloch line memory device of the present invention, and FIGS. FIG. 6 is a top view of the device having the main components of FIG. 3 and FIGS. DESCRIPTION OF SYMBOLS 1 ... Substrate 2, ... Magnetic film 2a ... Region showing perpendicular magnetization film 2b ... Region showing magnetic anisotropy or paramagnetism other than perpendicular 2b '... Guide paramagnetic region 4 ... Stripe domain 5 …… Bubble generation conductor 6 …… Bloch line control conductor 7 …… Chopping conductor H _B …… Bias magnetic field

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11C 11/14

Claims (1)

(57) [Claims] 1. A Bloch line memory device having a magnetic film exhibiting perpendicular magnetic anisotropy that stores a vertical Bloch line pair as a storage information unit on a domain wall of a stripe domain. A Bloch line memory device characterized in that a stripe domain is stabilized in a region exhibiting perpendicular magnetic anisotropy by providing a region exhibiting magnetic anisotropy or paramagnetism.