JP2759150B2 - Magnetic recording thin film and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording thin film applicable to high-density recording such as perpendicular magnetic recording and magneto-optical recording.

[Conventional technology and its problems] As a conventional polycrystalline high-density recording material, MnBi as a magneto-optical material is famous as an initial material, but has been put into practical use due to problems such as structural instability due to phase transition. Not.

In addition, polycrystalline materials containing Mn and Sb, such as MnSb and PtMnSb, have been studied as recording materials, and PtMnSb has attracted much attention in terms of the Kerr rotation angle. However, since these materials have an easy axis of magnetization in an in-plane direction and do not become a perpendicular magnetization film, the polar Kerr effect cannot be used, and thus these materials are not suitable for magneto-optical recording. Furthermore, since PtMnSb contains expensive Pt, there is a problem that the cost is high.

The present invention has been made in view of the above circumstances, and provides a magnetic recording thin film having an easy axis of magnetization perpendicular to the film surface, capable of high-density recording, and having a high SN ratio, and a method of manufacturing the same. With the goal.

[Means for Solving the Problems] The magnetic recording thin film according to the present invention comprises Mn (manganese), Al
A magnetic recording thin film comprising (aluminum) and Sb (antimony) as constituent elements, wherein a laminated structure in which first ultrathin layers made of Mn and Al and second ultrathin layers made of Sb are present alternately. None, wherein atomic diffusion occurs at a layer interface between the first ultrathin layer and the second ultrathin layer.

Further, the method for manufacturing a magnetic recording thin film according to
-Forming a thin film in which a first ultra-thin layer made of an Al alloy and a second ultra-thin layer made of Sb are alternately and periodically laminated, and heat-treating this thin film in vacuum to form an atomic layer between each layer; It is characterized by causing diffusion.

[Function] In the present invention, a thin film is formed by alternately and periodically laminating a first ultrathin layer made of a Mn-Al alloy and a second ultrathin layer made of Sb, and heat treatment is performed on each layer. Causes atomic diffusion to form a magnetic recording thin film having a composition represented by Mn _X Al _y Sb _Z described above. The magnetic thin film having this composition has an easy axis of magnetization perpendicular to the film surface, and can be applied to high-density recording of a perpendicular magnetic memory or a magneto-optical memory. Further, since the structure before the heat treatment is a structure in which ultrathin layers having different compositions are alternately laminated, the atomic diffusion due to the heat treatment does not occur over the entire laminated thin film but mainly only through the layer interface. Therefore, crystal grain growth is suppressed, and a thin film of fine crystals can be obtained.

EXAMPLES Hereinafter, the present invention will be described specifically.

The present invention is based on a magnetic thin film composed of a magnetic element Mn and Al and Sb. That is, an extremely thin Mn-Al alloy layer and an Sb layer are alternately laminated a plurality of times, and then heat-treated for a predetermined time, whereby Mn _X Al _y Sb _Z (x, y, z is z = 1− (x +
y). A magnetic recording thin film having a composition represented by the formula (1) is formed. In this case, 0.4 <x <0.5 and 0.4 <y
If <0.5, or 0 <x <0.08 and 0 <y <0.08, the residual magnetization ratio (M _r⊥ / M _r ) is 1 or more. That is, it is a perpendicular magnetization film having an easy axis of magnetization perpendicular to the film surface.

In this case, if the heat treatment temperature is set to, for example, 350 ° C. or higher, atomic diffusion occurs between the ultrathin layers, and Mn-Al-
A Sb crystal alloy forms. As described above, when atom diffusion occurs locally, grain growth is suppressed, and the crystal grains of the obtained thin film become fine.

Thus, since it is a perpendicular magnetization film and the crystal grains are fine, it exhibits excellent magnetic properties as a magnetic recording thin film. That is, high-density recording is possible, and a magnetic recording thin film having a high SN ratio can be obtained.

Incidentally, in the Mn _X Al _y Sb _Z, x is the case in the range of 0.08 ≦ x ≦ 0.4 _is, M r⊥ / M _r becomes smaller than 1. Therefore, x is set to 0.4 <x <0.5 or 0 <x <0.
It is preferable to set within the range of 08.

When such a magnetic recording thin film is formed on a substrate, various types of sputtering such as vacuum evaporation, DC sputtering, and RF sputtering can be used. When these films are formed, the thin film immediately after the film formation is in an amorphous state. In this case, a stable material, for example, glass can be used as the substrate.

In such a magnetic recording thin film, by changing the thickness of the ultra-thin layer, the number of layers and the heat treatment conditions,
Grain size and magnetic properties can be controlled over a wide range.

Next, a description will be given of a test example in which a sample is actually prepared and tested based on the present invention. FIG. 1 is a cross-sectional view showing a thin film formed by laminating ultra-thin layers on a substrate. First, the first ultrathin layer 3 made of MnAl and the second ultrathin layer 4 made of Sb are alternately and periodically laminated on a glass substrate 1 by RF sputtering to form a thin film 2. did. At the time of this sputtering, the MnAl alloy target and the Sb target are mounted in the RF sputtering device, the substrate is installed rotatably, the substrate is alternately positioned directly above each target, and RF power is alternately supplied to these targets Then, an extremely thin layer was laminated. In this case, the inside of the sputtering apparatus was set to a gas pressure of 1.0 × 10 ⁻³ Torr, and the substrate temperature was set to room temperature or 200 ° C.

In this way, the conditions and compositions of A1 to L2 are different.
Different types of samples were created.

Table 1 shows the set value of the thickness of the ultra-thin layer of each sample, the set value of the thickness of one cycle of the laminated ultra-thin layer, the number of layers, the composition of one cycle, and the thickness of one cycle obtained from the X-ray diffraction peak. 3 shows the substrate temperature and heat treatment conditions during sputtering. The heat treatment conditions for samples A2, B1, B2, D3, and F1 were changed in two stages.

Except for samples D2 and J2 which were sputtered at 200 ° C. among these samples, diffraction peaks due to interference of each layer were obtained in X-ray diffraction on the small angle side. That is, it was confirmed that these samples had a composition modulation structure. In addition, although the sample Al was sputtered at 200 ° C., the composition modulation structure was maintained. With such a composition modulation structure, the thickness of each layer can be detected by a diffraction peak. For example, in sample A2, an X-ray diffraction peak exists on the small angle side as shown in FIG. The thickness of one cycle from the peak was 33.8 °. The layer thickness was determined for other samples in the same manner. As shown in Table 1, for each sample, the layer thickness in one cycle after film formation almost coincided with the set value. In addition, it was confirmed by X-ray diffraction that the sputtered film at the substrate temperature of room temperature had no crystal-derived peak and was in an amorphous state. On the other hand, in the case of sputtering at a substrate temperature of 200 ° C., the presence of crystals was confirmed by X-ray diffraction at this time. In addition, samples other than the sample sputtered at a substrate temperature of 200 ° C. or higher did not show ferromagnetism at room temperature immediately after film formation.

After the heat treatment, the Mn-Al-Sb ferromagnetic crystal alloy was generated in each of the samples. This indicates that atomic diffusion has occurred between the ultrathin layers.

The crystal grain size determined from the broad X-ray diffraction peak of each sample was estimated to be 500 ° or less.

Next, the results of grasping the magnetic properties of these samples will be described. FIG. 3 is a graph showing the relationship between the Mn content (atomic%) of the Mn-Al-Sb alloy on the horizontal axis and the saturation magnetization intensity (emu) at room temperature on the vertical axis. . In the figure, open circles are samples heat-treated at 500 ° C for 5 hours, black circles are samples heat-treated at 370 ° C for 8 hours, and open triangles are 500 ° C after sputtering the substrate at 200 ° C.
5 shows a sample heat-treated for 5 hours (the same applies to FIGS. 4 to 6 below). These heat treatment temperatures are actual temperatures of the substrate. According to this graph, it was confirmed that the intensity of the saturation magnetization peaked when Mn was approximately 25 atomic%.

4 and 5, the horizontal axis represents Mn as in FIG.
Is the coercive force (O _e ) of the film at room temperature on the vertical axis, and the relationship is shown in FIG. And
FIG. 5 shows a case where a magnetic field is applied perpendicular to the film surface. Note that these bluffs show the case where the atomic ratios of Al and Mn are equal (that is, x = y). According to these graphs, especially when Mn exceeds 40 atomic% (that is, when x is 0.
4), it was confirmed that the coercive force when a magnetic field was applied perpendicular to the film surface increased.

FIG. 6 shows the _ratio between the residual magnetization M _rＭ when a magnetic field is applied perpendicular to the film surface and the residual magnetization M _r when a magnetic field is applied perpendicular to the film surface, with the Mn content plotted on the horizontal axis. _(M r⊥ / _M r)
5 is a graph showing the relationship between them. Here, if M _r⊥ / M _r is greater than 1, it is considered that the film is a perpendicular magnetization film. According to this graph, when the Mn content is more than 40 atomic% and when the Mn content is less than 8 atomic%, M _r / M _r becomes larger than 1, and a perpendicular magnetization film is obtained. That is, 0 <x <0.08 and 0.4 <x in Mn _x Al _y Sb _z
Then, it becomes a perpendicular magnetization film.

In addition, as a result of confirming the Kerr effect of these samples, a relatively large Kerr rotation angle (θ _k ) was obtained in each case, and particularly, when x <0.2, θ _k showed a large value of about 0.5 °.

Thus, in the magnetic thin film of Mn _x Al _y Sb _z , in particular,
In the case of 0.4 <x <0.5 and 0.4 <y <0.5, or 0 <x <0.08 and 0 <y <0.08, the crystal grains are fine and the film is a perpendicular magnetization film. The coercive force when a magnetic field is applied is large, and the Kerr rotation angle is large when x <0.08.
Therefore, in this composition range, high density recording characteristics are particularly good, and a high SN ratio due to noise reduction is expected because the crystal grains are fine.

[Effects of the Invention] According to the present invention, a magnetic recording thin film having an easy axis of magnetization perpendicular to the film surface and having a very small crystal grain size can be obtained. Such a thin film enables high-density recording and achieves a high SN ratio. As described above, according to the present invention, excellent characteristics can be obtained as a magnetic recording thin film, which is extremely useful.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which an extremely thin layer for forming a magnetic recording thin film according to the present invention is formed on a substrate, and FIG. 2 shows an X-ray diffraction pattern on the small angle side of the thin film immediately after film formation. Figure,
FIG. 3 is a graph showing the relationship between the Mn content of the thin film and the saturation magnetization at room temperature. FIGS. 4 and 5 are graphs showing the relationship between the Mn content of the thin film and the coercive force at room temperature. The figure is a graph showing the relationship between the Mn content of the thin film and the residual magnetization ratio. 1 ... substrate, 2 ... thin film, 3,4 ... very thin layer.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01F 10/12 H01F 10/12 41/16 41/16

Claims (3)

(57) [Claims] 1. Mn (manganese), Al (aluminum) and
A magnetic recording thin film containing Sb (antimony) as a constituent element, wherein the thin film has a laminated structure in which first ultrathin layers made of Mn and Al and second ultrathin layers made of Sb are present alternately. A magnetic recording thin film wherein atomic diffusion occurs at a layer interface between the first ultrathin layer and the second ultrathin layer. 2. A thin film in which a first ultra-thin layer made of an Mn-Al alloy and a second ultra-thin layer made of Sb are alternately and periodically laminated, and this thin film is heat-treated in a vacuum. And causing atomic diffusion between the respective layers. 3. The method according to claim 2, wherein said thin film is formed by sputtering or vacuum deposition.