JP3278655B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel magnetoresistive recording medium, and more particularly, to a novel type of magnetoresistive recording medium made of a material which has never been used as a magnetic recording medium. is there.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a medium in which magnetic fine particles are dispersed in a binder and coated on a substrate has been mainly used. The medium is gradually shifting to a medium having a magnetic film formed thereon. A thin film of ferrite or an alloy formed directly on the substrate by sputtering or vacuum evaporation is called a thin film type magnetic recording medium, which is used for ultra-high density recording recently required.

Incidentally, as one of means for increasing the density, a magnetic head using a thin film magnetoresistance effect has been developed and put to practical use. This has an advantage that it has remarkable magnetic sensitivity and can remarkably improve the recording density as compared with an electromagnetic induction type magnetic head used for conventional magnetic recording.

[0004] Such a magnetic head is composed of Fe, Co, N
A multi-layer structure of a ferromagnetic metal composed of a 3d transition metal element such as i or an alloy thereof and a non-magnetic metal such as Cu, wherein the spin-dependent conduction of the ferromagnetic metal layer through the non-magnetic metal layer This is basically different from a conventional electromagnetic induction type magnetic head in that a change in rate, that is, a giant magnetoresistance effect is used.

On the other hand, it is possible to produce a structure exhibiting a giant magnetoresistance effect by forming crystals on a semiconductor by epitaxial growth, or to control the electron concentration of the semiconductor from the outside and utilize the change in spin-dependent conduction. Attempts have been made to obtain magnetic heads having advanced functions, but they have not been realized yet.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a completely new type of magnetoresistive recording medium utilizing the giant magnetoresistance effect.

[0007]

The present inventors have conducted intensive studies to develop a magnetoresistive recording medium utilizing the giant magnetoresistive effect, and as a result, the conventional ferromagnetic / semiconductor multilayer film has become clear. The reason why the giant magnetoresistance effect was not exhibited is that these are combinations of simple substances, for example, a combination of F and Si, so that a reaction between the simple substances occurs near their interface, and the interface structure is roughened. Therefore, the present inventors have found that a structure exhibiting a giant magnetoresistance effect can be obtained by forming a stable interface by combining a metal compound ferromagnetic material and a compound semiconductor, and based on this finding, led to the present invention. Was.

That is, the present invention provides a magnetoresistive recording medium comprising a substrate and a multilayer laminate of a combination of a metal compound magnetic material / compound semiconductor / metal compound magnetic material provided on a substrate.

[0009]

Next, the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an enlarged sectional view showing an example of the structure of a magnetoresistive recording medium of the present invention, in which a first metal compound magnetic layer 2, a compound semiconductor 3, and a second metal compound magnetic material are provided on a substrate 1. Layers 4 are sequentially stacked.

The substrate in the magnetoresistive recording medium of the present invention can be arbitrarily selected from non-magnetic base materials conventionally used as substrates for magnetic recording media. That is, in the case of video tapes and video discs, plastics having appropriate flexibility and hardness, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyether ether ketone (PEE)
K), polyimide, polyimine imide, polycarbonate (PC), aramid resin, and the like, and in the case of a video disc, aluminum, silicon, an Al—Mg alloy, and the like. Particularly, when each layer is formed by epitaxial growth, GaAs substrates are preferred. As in the case of the conventional magnetic recording layer, these substrates are provided with an underlayer, for example, a silicon oxide SiO _x (where 1.8 is used).
0 ≦ x ≦ 1.95).

The magnetoresistive recording layer of the present invention is basically composed of a three-layer structure of a combination of a metal compound magnetic material / compound semiconductor / metal compound magnetic material. it can. As the metal compound magnetic material, a metal compound of a group 3B element of the periodic table and a group 7A element such as MnGa and MnAl is used, and as a compound semiconductor, GaAs, GaSb, ZnSe, ZnT
e, CdSe, CdTe, AlAs, AlSb, InA
s, InSb, PbSe, PbTe, Ga ₂ Se ₃ , Al
Periodic Table 2B or 3B element such as ₂ Se ₃ and 5B
Compounds with Group 6B and Group 6B elements are used.

The thickness of the first metal compound magnetic layer in the magnetoresistive recording layer of the present invention is usually 10 to 100 nm, preferably 15 to 25 nm, and the thickness of the compound semiconductor layer is usually 1 to 100 monolayer (ML). , Preferably 2 to 30
ML, the second metal compound magnetic layer is usually 5 to 50 nm,
Preferably, it is selected in the range of 7 to 20 nm. Here, the monolayer (ML) is a unit based on the thickness of one atomic layer of the material constituting each layer.

The magnetoresistive recording medium of the present invention is advantageously produced by an epitaxy method. That is, first, a metal compound magnetic material is epitaxially grown on a substrate plane to form a magnetic material layer having a thickness of 10 to 100 nm, and then a compound semiconductor is formed thereon with a thickness of 1 to 100 ML. A metal compound magnetic material is formed to a thickness of 5 to 50 nm to form a three-layer sandwich structure.

The magnetoresistive recording medium thus formed exhibits a giant magnetoresistive effect in which the electric resistance changes depending on the direction of magnetization of the metal compound magnetic layer, and the rate of the change is about 1%. That is a sufficiently large value. Also,
Since this change occurs rapidly and does not change with time, magnetic information can be recorded using this giant magnetoresistance effect. In the magnetoresistive recording medium of the present invention, when the first metal compound magnetic material and the second metal compound magnetic material are composed of the same combination of elements, the ratio of one element is controlled during epitaxial growth. By doing so, the coercive force can be changed, and the thickness of each layer can be arbitrarily changed by controlling the film forming conditions of each layer, for example, the temperature of the substrate and the raw material. As described above, the magnetoresistive recording medium of the present invention can be used as an information carrier or a magnetic head, like the conventional electromagnetic induction type recording medium.

[0015]

Next, the present invention will be described in more detail with reference to examples.

Example 1 2 linked by UHV load lock system
GaAs using molecular beam epitaxy (MBE)
s and MnGa are epitaxially grown to form MnGa / GaAs / Mn on a GaAs (001) substrate.
A three-layer structure of Ga was formed. At this time, the composition of the first metal compound magnetic layer was adjusted to Mn ₅₄ Ga ₄₆ and the composition of the second metal compound magnetic layer was adjusted to Mn ₆₀ Ga ₄₀ by changing the flux composition of the Mn supply source. Thus, the GaAs
Mn ₅₄ Ga ₄₆ layer of 20 nm thickness on s substrate, 12 M thickness
A magnetoresistive recording medium having a sandwich structure in which an L GaAs layer and a 10 nm thick Mn ₆₀ Ga ₄₀ layer were sequentially laminated was obtained. For this, a magnetic-circular-dichroism (MCD) curve at room temperature was measured, and the result is shown in FIG. This MCD is defined by θ in the following equation.

[0017]

(Equation 1) (Where R ⁺ and R ^- are the reflectivity for σ ⁺ and σ ^- polarized light, respectively).

Further, a change in the magnetic field of the resistance when a current at room temperature was passed in parallel to the sample surface was measured and is shown in FIG. The vertical axis in this figure indicates the difference between the resistance value R (H) at each magnetic field and the resistance value R (0) at zero magnetic field, and the resistance value R at zero magnetic field.
The magnetic resistance (%) divided by (0), and the horizontal axis is the magnetic field (unit T: Tesla). As is clear from this figure, when the magnetizations of the first metal compound magnetic layer and the second metal compound magnetic layer indicated by white and black arrows are antiparallel, the resistance value decreases by about 1%, and The change in resistance observed at 0T and 0.5T is very sharp.

Example 2 A magnetoresistive recording medium was manufactured in the same manner as in Example 1, except that the thickness of the GaAs layer was changed to 16 ML. The MCD hysteresis curve of this is shown in FIG.

[0020]

The present invention is a magnetoresistive recording medium having a structure which has not been known so far, and is suitable for high-density recording because it does not change with time and responds sensitively to a magnetic field change.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of one example of a magnetoresistive recording medium of the present invention.

FIG. 2 is a graph showing an MCD hysteresis curve of the sample obtained in Example 1.

FIG. 3 is a graph showing a change in the magnetic field of the resistance of the sample obtained in Example 1.

FIG. 4 is a graph showing an MCD hysteresis curve of the sample obtained in Example 2.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-180479 (JP, A) JP-A-10-173253 (JP, A)

Claims (4)

(57) [Claims] 1. A magnetoresistive recording medium comprising a substrate and a multilayer laminate of a combination of a metal compound magnetic material / compound semiconductor / metal compound magnetic material provided on a substrate. 2. The magnetoresistive recording medium according to claim 1, wherein the metal compound magnetic material is MnGa. 3. The compound semiconductor according to claim 1, wherein the compound semiconductor is GaAs.
Or the magnetoresistive recording medium according to 2. 4. A metal compound magnetic material comprising two kinds of metal compounds composed of the same element and having different compositions.
Or a magnetoresistive recording medium according to 3.