JPS63100172A - Superlattice material and its production - Google Patents

Abstract

PURPOSE:To produce a superlattice material having excellent magnetic characteristics by laminating and forming many single-layer films which consists of elements different from an alloy underlying material having an ordered phase and has the artificial period corresponding to the period structure of said ordered phase onto said underlying material. CONSTITUTION:The alloy having the existing ordered phase is used as the underlying material and the many single-layer films are formed thereon in parallel therewith by a thin film forming means such as vacuum deposition method. The above- mentiopned single-layer films are constituted of the elements different from the element constituting the alloy of the above-mentioned underlying material. The elements which satisfy an adequate bond energy relation are selected. The superlattice material of the multi-layered material consisting of the many single-layer films which consist of the above-mentioned different materials, are formed in correspondence to the period structure of the ordered phase of the above-mentioned underlying material and have the artificial period maintaining the periodic structure of the ordered phase is thereby obtd. The above-mentioned material has excellent magnetic characteristics such as anisotropic magnetic field and Kerr rotating angle and is adequate for perpendicular recording media and magneto-optical recording materials.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a superlattice material in which the base material of a multilayer material is a regular layer and artificial periods exist within the plane of a single layer, and a method for manufacturing the same. In particular, the present invention relates to a superlattice material suitable for perpendicular magnetic recording media and heads with controlled magnetic anisotropy, and a method for manufacturing the same.

[Conventional technology]

Conventionally, regarding superlattices, the period of the artificial lattice exists only in the direction perpendicular to the monolayer film surface, as discussed in pages 1 to 8 of the Japan Society for Applied Magnetics, 43rd Research Meeting Materials (1986). are doing. In other words, when a superlattice is grown on a substrate, it is a material that has an artificial period in the direction parallel to the growth direction, and no consideration has been given to the artificial period in the direction perpendicular to the growth direction, that is, in the plane of the monolayer film. .

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, the in-plane period of a single layer of a multilayer film is not considered, and the amount of variation in the interatomic distance is small. In other words, a superlattice having an artificial period only in the direction perpendicular to the surface of the monolayer film has a small amount of change in the interatomic distance in the direction perpendicular to the surface of the monolayer film. In this way, it is difficult to change the properties of a bulk material in a material with a small amount of change in interatomic distance, even though it has an artificial periodic structure.

SUMMARY OF THE INVENTION An object of the present invention is to provide a superlattice material and a method for manufacturing the same that eliminate the above-mentioned drawbacks and have magnetic properties that cannot be obtained with bulk materials or thin film materials.

[Means for solving problems]

The above purpose is to use an alloy with regularity in the atomic arrangement as a base material for a multilayer film, and to use the regular periodic structure of this base material to form an artificial period within the surface of the single layer film. This is achieved by

That is, the superlattice material of the first invention of the present application is composed of a base material made of an alloy having ordered properties, and an element different from the element constituting the alloy of the base material, and the superlattice material is placed on the base material in parallel thereto. The second invention of the present application is characterized by being made of a multilayer material composed of a large number of single-layer films formed corresponding to a periodic structure for rules and having artificial periods that maintain the periodic structure for rules. The superlattice material according to the first invention is further characterized in that it is made of a multilayer material having an artificial periodicity on the vertical plane of the single layer film. Further, in the method for producing a superlattice material according to the third invention of the present application, an existing alloy having a regular structure is used as a base material, and the element is different from the element constituting the alloy of the base material, and the required relationship between the elements is Selecting an element that satisfies the bond energy relationship, and using an appropriate thin film forming means, an artificial period made of the above-mentioned element and corresponding to the periodic structure for the rule, and maintaining the periodic structure for the rule. A multilayer material is obtained by forming a large number of single-layer films having the following properties in parallel on the base material.

Below, the configuration of the invention of the present application will be explained in more detail.

The crystal structure of alloys has two types: ordered and disordered.When the atoms that enter a certain position are fixed and exist stably, it is called ordered, and when it is not fixed, it is called disordered. In ordered materials, the arrangement of atoms is periodic, and if a material with regularly arranged atoms and a certain periodic structure is used as a base material for a multilayer material, it will not normally form regular materials and will be stable. Even if the material does not exist in a normal state, the period can be freely controlled to form a layer with an artificial period that maintains the periodic structure in the regular soil. The following can be used for rules:

CuA1. Cu,,Aj! , CuAu, Cu3A
u, Cu3Ga+Cu3Ge.

CuPd, Cu5Pd, CuAt, CuPt3.
Cu5Sn+ Cu5Sn, CuZn.

uZns CrGaa, Cr3Ga, CrGe, CrGe
3. Cr, NbTiAl3. Ti3Al, Ti,
A1. Ti2Cr, T1Cr2. T1Cu:+.

Ti2Cu+ Ti3Cu, TiMnz, TtzM
n, TizZnMnCr, MnGa4. Mn,G
a+ Mn5Ge+ MnNi, MnN13. Mn
Ti+nTiz The superlattice material of the present invention will be specifically explained. For example, when AB and compounds made of binary alloys are used for regulation,
As shown in FIG. 1, the atomic arrangement of the A B 4 compound on the closest atomic plane is arranged in the order ABBBBA . . . as shown in 1. Using this rule as a substrate, approximately the same number of C as A elements
Depositing elements. At this time, the C element must be arranged near the A element. For this purpose, element C must have a stronger bonding force with element A than element B. Here, when the bond energy between atoms is expressed by E, there are 10 types of E in the four atoms in FIG.

In order to enable growth as shown in Figure 1, the C element must be
It is necessary to grow V-W (volmer-@eber) type for the elements, and for the D element to grow in a single layer with respect to the B element. In order for these two types of growth to occur, Ell<Eo
o+ EaA>Ecc must be satisfied. Also the first
When an A B a compound as shown in the figure is used as an ordered phase, E Since it exists in the layer film, E on > E cc. After all, in order to obtain a periodic structure as shown in FIG. 1, the following binding energy relationship must be satisfied: EDD>Elm>Eaa>ECC (1). The relationship in equation (1) depends on the type of ordered phase, and in the case of A B s ordered phase, Ell>EAA>Ecc>EDIl (2)
becomes. Furthermore, in order to produce a superlattice material with the shortest artificial period within the plane of a single layer film, an ordered phase of an AB compound as shown in FIG. 2 is used. In this case, the C element on the A element and the D element on the 8 elements need to grow in a VW type, EAA>Ecc, Egg>Eoo (3)
The conditions are as follows.

An example of a regular lattice other than the above case is a D Oy type ordered phase. The relational expression of binding energy in this case is (3)
According to the formula.

The elements of the superlattice are determined based on formulas (11 to (3)) as described above. Next, the manufacturing conditions will be described.

In order to produce a superlattice material having an artificial period as shown in FIGS. 1 and 2, it is necessary to control the production conditions, particularly the ultimate vacuum degree, substrate temperature, substrate material, and vapor deposition rate. The ultimate degree of vacuum was 1×1 O −9 Torr or lower, and the substrate temperature was lower than the regular-irregular transformation point. Further, the substrate material was selected to be one in which the first ordered phase easily grows as a single phase, and the deposition rate was set to 0.1 person/llln or less. This evaporation rate makes it possible to evaporate elements whose number of atoms corresponds to the ratio of constituent elements of the regular lattice.

The superlattice material of the present invention can be used for perpendicular magnetic recording media, magnetic heads,
It is suitable for use in magnetic disks, magneto-optical recording materials, etc.

[For production]

In order to produce the superlattice material of the present invention, it is necessary to select an ordered phase that can control the crystal growth mechanism and elements for the growth phase to be grown thereon. An ordered phase like 1 in Figure 1 is placed on a substrate, and the first layer is C element (5) and A element (3).
grow on top. At this time, in order to place C element directly above A element, the bond energy between A element and C element must be stronger than the bond energy between B element and C element, so the conditions EAc〉〉E, c are required. It is. Next, considering the growth mechanism, the C element must be stacked one atom at a time on the A element, and conditions are required that prevent a plurality of C elements from growing in a single layer. Conversely, element D must grow in a single layer on 8 elements, so the binding energy conditions are E + u+ < E DD, E cc < E
It becomes like Aa. A B Since the close-packed plane of the a-type regular lattice does not form A-atom pairs as shown in Figure 1, 1, E
Since there is a relationship 1111 > E AA, a condition like the +11 equation becomes a condition for forming an artificial period as shown in FIG. Further, in the case of AB, a pattern ordered phase, since ABABAB... is included in the closest packed plane of the ordered lattice, the B element on the 0 element and the C element on the A element need to grow in a VW type.

In addition, the AB3 type regular lattice has two types of repeating arrangements: the ABABAB... arrangement and the atomic arrangement of only B atoms.
EAA<Ell. From the above, in order to obtain a superlattice material having an artificial periodicity similar to that of AB3 type on an AB3 type regular phase, the conditions shown in Table 1 are required.

(This page, blank space below) Table 1 Furthermore, in order to create an artificial period in the plane of a monolayer film using an AB type or DO3 type ordered phase as a substrate, the bond energies shown in Table 1 are required, taking into account the crystal growth mechanism. Find the conditions for The artificial period in Table 1 is the case where element C is grown on element A and element D is grown on 8 elements as shown in Figure 1.2.
Even when growing C element on element 8, the bonding energy conditions can be easily determined.

The magnitude relationship of E AA + E ll + E CC + E DD can be determined from the observation results of the film growth mechanism when each single metal is used as a substrate. For example, Fe
When Cu is deposited using the substrate as a substrate, the result that E CuCu <E FlIFe is obtained since Cu performs VW type growth. Also, when Cu is deposited using Ni as a substrate, Cu grows as a single layer, so E CuCu > E
Be like NiNi. Therefore, E FIIFII >
It can be seen that the order is E CuCu > E NiNi.

The conditions for producing superlattice materials include ultimate vacuum, substrate temperature,
and that the deposition rate is important. The reason for this will be explained below. Thin film growth mechanisms can be roughly divided into two types: nucleation and growth mode and monolayer growth mode. The former is called Volmer-Weber type growth (V-W type), and these growth mechanisms depend on binding energy under ideal conditions. This ideal condition can be obtained by controlling the film growth conditions. In order to find this condition, an Fe film was grown on an Fe single crystal. If the same metal is used as the substrate and the film is grown under ideal conditions, it will grow as a single layer. Therefore, it is only necessary to find conditions for growing a single layer of Fe film using Fe single crystal as a substrate. LEED (low energy electron diffraction) and RHEED (high energy reflected electron diffraction) are methods for determining that monolayer growth is occurring. Figure 3 shows O,OS on (110)Fe at room temperature.
The RHEED pattern is shown when Fe with a purity of 99.99% is deposited at a deposition rate of 1 person/min. (a) to td) are obtained by changing the vacuum degree immediately before vapor deposition, and the respective vacuum degrees are (a) 5 X 10-”Torr, (b) I
X 10-@, (C)5 Xl0-', (d)
I Xl0-''. (a) has poor crystallinity, has a random growth direction, and is accompanied by nucleation.

(b) does not involve nucleation, but the growth direction is not constant and gas molecules are adsorbed between the substrate and the growth layer (fa)
The background is also high. In (C), the background is low and the growth is almost a single layer, but the peak is narrow due to poor matching between the underlying atomic arrangement and the growth layer. (d) is an almost perfect monolayer grown film with a sharp peak of 0.
From the above results, the degree of vacuum for monolayer growth is < I
It can be seen that it must be set to Xl0-'Torr.

Figure 4 uses the same substrate and deposition source as Figure 3, and the deposition rate is 0.
．． RHE when changing substrate temperature at 05 people/min
This is an ED pattern. The temperature of each substrate is la) 8
00℃, (b) 750℃, (C) 700℃,
+d) 650°C. It can be seen that the lower the substrate temperature, the easier it is to grow a single layer. This result shows that it is possible to form a single layer film sufficiently if the substrate temperature is around room temperature.

However, when using an ordered phase as a substrate, if the substrate is heated above the ordered-disorder transformation point, the ordered phase will decompose and the atomic arrangement will become random. Disturbance occurs in the atomic arrangement of the superlattice material in the plane. Therefore, the substrate cannot be heated above the regular-disorder transformation point.

FIG. 5 shows RHEED patterns when the deposition rate is varied under the same experimental conditions as in FIG. 4 at room temperature. The deposition rate is (al 0 , 5 persons/lll1n, (b) 0.
3 people/lll1n.

(C) 0.1 person/llln, and it can be seen that monolayer growth is more likely to occur as the deposition rate decreases. (a)
(In bl, nucleation occurs and the diffraction peak becomes broad, but when the deposition rate is 0.1 person/min, almost complete monolayer growth occurs.

As shown in FIGS. 3 to 5, the conditions for single-layer growth of the Fe film are: degree of vacuum < I Xl0-'Torr, substrate temperature: regular-irregular transformation point, and deposition rate <0.1 person/win. Therefore, in order to obtain the superlattice material according to the claims of the present invention, the film must be grown under vapor deposition conditions that satisfy the above conditions.

〔Example〕

Examples of the present invention will be described below. Ag4 type Ni4Mo was selected as the ordered phase, and the grown layer was made of a FeAg alloy in consideration of the bond energy E. The vapor deposition conditions are shown in Table 2.

Table 2 The reasons for determining these deposition conditions are as described above. N
Si single crystal + as a substrate when depositing i4Mo ordered phase
There are 5iO1+ glass substrates and metal single crystals, but when a St single crystal is used as a substrate, the first layer of Ni on the substrate
4M0 does not result in complete monolayer growth. Therefore, Ni, M
The crystal orientation at the surface of o depends on the film thickness * N1J
As shown in Figure 8, the intensity of (111), which is the closest-packed plane of Since this does not occur, it can be seen that N1Jo having a film thickness of 400 Å or more can be manufactured under the conditions shown in Table 2. This N1Jo
A FeAg alloy with a thickness of approximately 2000 ml was deposited on the film under the deposition conditions shown in Table 2, and the saturation magnetization (B,) per Fe atom was measured using a vibrating sample magnetometer (VSM). The results are shown in FIG. The heating temperature in Fig. 6 is for Ni, Mo
It shows the heating temperature of the substrate before vapor deposition, which is 400℃.
If it is more than that, the magnetic moment of Fe increases. This is because defects are generated on the surface of the Ni4Mo film as deposited at room temperature, and by heating to reconfigure the surface atoms, the close-packed atomic arrangement on the Ni4Mo surface is completed. When N1Jo was heated in lh oil at 500° C. and a FeAg alloy was deposited using it as a substrate, a diffraction peak as shown in FIG. 7 caused by in-plane periodicity was generated in transmission X-ray diffraction. Therefore, it has become clear that Fe atoms and Ag atoms have an artificial period in a plane parallel to the substrate. Fe and Ag or FeAg used for vapor deposition here
The alloy had a purity of 99.999% or more and was produced by determining the deposition rate under the deposition conditions shown in Table 2 and controlling the shutter opening time. The maximum shutter opening time is 0.
It can be controlled with an accuracy of 0.5 seconds.

In addition to binary vapor deposition, we also attempted vapor deposition of a single FeAg alloy. Figure 6.7 shows the case of binary evaporation, but when an alloy is used as the evaporation source (Fe:Ag, 4:1), the value of saturation magnetization per Fe is affected by the evaporation rate, and As shown in Figure 9, B3 increased more than bulk Fe at 0.03 persons/win or less. The reason why 83 decreases as the deposition rate increases is because
This is because the high mobility of Fe and Ag atoms on a regular lattice causes disturbances in the periodicity, and during vapor deposition, the size of the clusters of Fe and Ag atoms that reach the substrate from the vapor deposition source varies. be.

As ordered alloys, N1=Sn of Ag3 type, F of AB type
Using eSn and DO3 type Fe5Al as substrates, Co (99,999%) and Ag (99,999%) were added under the conditions shown in Table 2.
999%) were deposited alternately. FIG. 10 shows the vertical coercive force (Hc,) of the fabricated thin film. The N9 process increases as the film thickness increases, and at a film thickness of 0.4 μm, it becomes 300 to 6000 e regardless of which substrate is used. In addition, HC depends on the period of the ordered phase, and when FeSn with an ABAB... arrangement is used as a substrate, the HCJL is high, and in the case of a regular phase with a long period like Ni3Sn, H
C is lower.

Figure 11 shows Fe, C using FeSn and Fe1^l as substrates.
The Hc value of the Fe--Cu film is shown when u (99,99%) is alternately deposited under the deposition conditions shown in Table 2. In Fe-based alloys, the anisotropy energy is smaller than that of Co-Ag-based alloys, which is smaller than Hc and is about 10 to 2000. In this case as well, it depends on the period of the ordered alloy, and if an ordered phase with a short period is used, IIC
It can be seen that the construction also becomes larger.

Anisotropic magnetic field HI1 of Co-Ag alloy thin film measured in FIG. L is shown in FIG. HKJL also depends on the film thickness and the period of the ordered phase, and the thicker the film and the shorter the period of the ordered phase, the larger on becomes. The HwlO value is over 30,000e and is currently attracting attention. This value is nearly twice that of the CoCr1 film, and its application to perpendicular magnetic recording media can be considered.

Furthermore, the Kerr rotation angle (θK) of the Co-Ag superlattice material shown in FIG.
FIG. 13 shows the results of measurement using a maximum effect measurement device using a light source as shown in FIG. ) of the FeSn ordered phase-ordered Co-Ag superlattice material with the highest lcL is 1.0 ~
It is in the range of 1.7°. In particular, C at a film thickness of 0.4 μm
The o -Ag superlattice material has an angle of about 1.5°, which is higher than that of MnB1, etc., and is promising as a magneto-optical recording material.

〔Effect of the invention〕

According to the present invention, it is possible to control the periodicity within the crystal growth plane in a multilayer material, and it is possible to produce a film with an anisotropic magnetic field of 30,000 e or more.

In addition, the Kerr rotation angle is 1.0 to 1.7°, which was different from the conventionally developed MnB1. It is a larger material than rare earth transition metal amorphous, garnet, barium ferrite, etc.

Therefore, it can be applied to perpendicular recording media and magneto-optical recording materials.

[Brief explanation of the drawing]

Figure 1 shows element C on a base material made of A B a compound.
A diagram showing a state in which an ordered phase with an artificial period consisting of elements C and D is formed in a single-phase film surface. Figure 2 shows an ordered phase having an artificial period consisting of elements C and D on a base material made of an AB compound Figure 3 is a diagram showing the state in which is formed in a single phase film.
RHEE when Fe with a purity of 99.99% is deposited on (110) Fe at room temperature at a deposition rate of O,OS person/win
Figure 4 is a diagram showing the D pattern, and Figure 5 is a diagram showing the RHEED pattern when the same substrate and evaporation source as in Figure 3 are used, and the substrate temperature is varied at a deposition rate of 0.05 people/win. Figure 6 shows the RHEED pattern when the deposition rate is varied under the same experimental conditions as in Figure 4 at room temperature. Figure 7 shows the results of measuring the saturation magnetization (B,) of Ni4Mo at 500°C for 1 h.
Fig. 8 is a diagram showing the results of transmission X-ray diffraction when heating and using this as a substrate to deposit a FeAg alloy.
Figure 9 shows the relationship between the film thickness of N1Jo and the (111) strength of N1Jo.
Figure 10 shows the relationship between the deposition rate of 4:1) and the value of saturation magnetization per Fe.
Using eJl as a substrate, Co (99,999%) and Ag
Figure 11 is a diagram showing the vertical coercive force (HcL) of a thin film fabricated by alternately depositing Fe (99,999%).
Fe, Cu (99,
99%) was alternately deposited under the deposition conditions shown in Table 2.
12 is a diagram showing the anisotropic magnetic field H of the Co-Ag alloy thin film measured in FIG. 11, and FIG. 13 is a diagram showing the -The Kerr rotation angle (θK) of the Ag superlattice material was determined by the He-Ne laser (λ
It is a figure which shows the result of measurement using the best possible effect measuring device using a light source of -633 nm).

Claims (1)

[Scope of Claims] 1. A base material made of an alloy having an ordered phase, and a periodic structure of the ordered phase formed on the base material and parallel to the base material, comprising an element different from the element constituting the alloy of the base material. 1. A superlattice material comprising a multilayer material formed from a large number of single-layer films having an artificial period that maintains the periodic structure of the ordered phase. 2. A base material made of an alloy having an ordered phase, and a base material made of an element different from the element constituting the alloy of the base material, and formed on the base material in parallel with this, corresponding to the periodic structure of the ordered phase. , a large number of single-layer films having an artificial period that maintains the periodic structure of the ordered phase, and a multilayer material having an artificial period on a vertical plane of the single-layer film. . 3. The superlattice material according to claim 1 or 2, wherein a ferromagnetic ordered phase is used as the ordered phase. 4. The superlattice material according to any one of claims 1 to 3, characterized in that the superlattice material has a high saturation magnetic flux density and perpendicular magnetic anisotropy. 5. Using an existing alloy having an ordered phase as a base material, selecting an element that is different from the elements constituting the alloy of the base material and satisfying the required bond energy relationship between the elements,
Using an appropriate thin film forming means, a large number of single-layer films made of the different elements, formed corresponding to the periodic structure of the ordered phase, and having an artificial period that maintains the periodic structure of the ordered phase are applied to the base material. 1. A method for producing a superlattice material, which comprises forming a superlattice material in parallel on top to form a multilayer material. 6. The method for producing a superlattice material according to claim 5, wherein the thin film forming means is a vacuum evaporation method.