JPS6148763B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic garnet single crystal film grown on a non-magnetic (110) gallium garnet substrate and having orthorombic anisotropy in which the axis of easy magnetization is perpendicular to the film surface. Bell System Technical Journal
System Technical Journal) Volume 58 No. 6 No. 2
The valve magnetic domain element using a dual conductor pattern (D, C, P), which was announced by Bobek et al. on page 1453 (1979), is different from the conventional valve magnetic domain element. Features include: i) no need for a coil for generating a rotating magnetic field, (ii) high-frequency drive of the valve magnetic domain, and (iii) the ability to miniaturize the diameter of the bubble magnetic domain, improving the storage density of the device. have. However, in putting this device into practical use, it is important to control the domain wall state of the bubble magnetic domain existing in the garnet film material and to use only S=0 bubbles. As shown in FIG. 7-7 of the above paper, the margin for bubble transfer decreases when S=1 bubbles are mixed. As a method to solve this problem, it has been proposed to use a material that has orthorombic anisotropy, in which the axis of easy magnetization is perpendicular to the film surface and also has magnetic anisotropy within the film surface. In materials with orthorombic anisotropy, if the anisotropy is sufficiently large in the film plane, the domain wall state of the bubble domain is S = 0, as is clear from the example of orthoferrite.
Only. Using a bubble magnetic domain with only S=0 allows (i) the process of hard bubble suppression to be omitted, and (ii) high-frequency drive of bubbles, even in devices that use a normal permalloy pattern instead of a conductor pattern. (iii) There is no breakdown in transfer speed during stripe magnetic domain transfer in the stretcher section. In addition, when using a magnetic garnet film as an element for reproducing information from a magnetic recording medium by magnetic transfer and optical reading, it is necessary to
-26 (1979), p. 29, as long as conventional materials are used, the usable frequency band is 1 to 3 MHz due to the limited domain wall movement speed. However, for use in home VTRs, it is necessary to expand the frequency band to 6MHz. If an orthorombic anisotropic material is used in such an element, the maximum movement speed of the domain wall will be significantly improved compared to the 25 to 30 m/sec of ordinary materials, and the frequency band can be expanded to 7 MHz. Furthermore, if an orthorombic material is used in the laser beam deflection element, the driving frequency can be improved. Materials with orthorombic anisotropy cannot be obtained from (111) garnet films, which are common bubble materials. The magnetic symmetry of the (111) film is uniaxial. Therefore, even if hard bubbles are suppressed in this film, S=0 bubbles and S=1 bubbles coexist, and the film cannot be used as a material for a conductor pattern element with a wide margin width. (110) Orthorombic anisotropy occurs in garnet wave phase epitaxial films. Applied by Wolfe et al., Physics Letters Vol. 29, No. 12, p. 815 (1976)
As shown in the paper of It is necessary to satisfy the relationships shown in the following first and second equations. B′<0 (1) B′<−2A′ (2) However, in many garnets,
The value of A'/B' is approximately -2, and when grown on a nonmagnetic garnet substrate with a (110) plane, the direction perpendicular to the film surface does not become the axis of easy magnetization. Therefore, it is important to find a garnet film composition and manufacturing conditions that can provide a (110) garnet film having orthorombic anisotropy that simultaneously satisfies the first and second equations for double conductor pattern bubble elements and This is most important for the practical application of magnetic transfer/optical readout elements with a wide frequency band or laser beam polarization elements that can be driven in a high frequency range. Furthermore, I.E.E. Transactions on Magnetics (IEEE Trans.
Mag) Paper published by Breed et al. in MAG Volume 13, Page 1087 (1977) and Figure 25 Proceedings of the Applied Physics Association Lecture Conference Lecture No. 30a-F
-5 As is known from the paper published by Makino and Hidaka on page 558 (1978), (110) garnet films generally have a large coercive force Hc and cannot guarantee stability when used as a bubble element. Sometimes. In addition, in the material published by Breed et al.
Both the anisotropic energy Ku perpendicular to the film plane and the anisotropic energy Δ in the film plane are mainly due to strain-induced anisotropy. For this purpose, the difference in lattice constant between the film and the substrate and the lattice constant of the garnet film must be made extremely large. This not only causes coercive force, but also means that the magnetic properties are likely to change due to distortion caused by various element patterns deposited on the garnet film. Localized strain in the garnet film causes bubble malfunction. The object of the present invention is to provide a double-conductor patterned bubble element, a magnetic transfer/light readout element with a wide frequency band, and a laser beam deflection element that can be driven at high frequencies, which have an easy axis of magnetization perpendicular to the film surface, Another object of the present invention is to provide a (110) garnet film which has a low coercive force and can generate the required magnetic anisotropy mainly through growth-induced anisotropy without introducing strain into the film. The present inventors have developed (Y _{1 -x Tm x ) 3-y} Bi _y Fe _5-z (Ga _{1 -w} Al _w ) _z O ₁₂
(However, 0≦x≦1, 0.0S≦y≦0.7, 0.9≦z≦
It has been discovered that a garnet single crystal film having a composition expressed by 1.35 and 0≦w≦1 has orthorombic anisotropy with an axis of easy magnetization perpendicular to the film surface, leading to the present invention. The present invention will be explained in detail below using Examples. Example 1 Using melt composition 1 shown in Table 1, Y _{1 . 3} was deposited on a (110) Gd ₃ Ga ₅ O ₁₂ substrate at a temperature of 865°C.
When a Tm ₁ . ₃ Bi ₀ . ₄ Fe ₃ . ₇ Ga ₁ . ₃ O ₁₂ garnet LPE film was grown, it became an orthorombic anisotropic bubble material with the [110] axis perpendicular to the film surface as the axis of easy magnetization. . The magnetic properties of this LPE film are shown in Table 2. The anisotropic energy Ku between the easy axis of magnetization [110] and the intermediate axis of magnetization [001], and the intermediate axis of magnetization and the hard axis of magnetization [1] in this LPE film.
10] was measured using a ferromagnetic resonance device, and it was found that Ku=+
4800erg/cm ³ and △=+10700erg/cm ³ were determined. The relationship between Ku and △ and the already described A′ and B′ values is defined by the following equations (3) and (4). A′=−Ku+△ (3) B′=−2(Ku+△) (4) From this, A′=5900erg/cm ³ and B′=−31000
erg/cm ³ , satisfying equations (1) and (2). The domain wall state of the bubble domain in this material is S=
0, and all bubbles moved straight against the magnetic field gradient. The figure shows the results of blotting the bubble movement speed against the driving magnetic field. From this figure, mobility is μ
w=910 cm·sec ⁻¹ ·O _e ⁻¹ , and the bubble movement speed does not show saturation even at 5000 cm/sec. Since the bubble diameter is approximately 5 μm, this material allows bubble drive at 2.5 MHz or higher. The coercive force was H _c =1.4O _e using the relationship H _c =π/8ΔH _c from the intercept of the X axis in the figure, ie, the minimum driving magnetic field ΔH c of the bubble. This value is extremely low compared to the coercive force value of conventionally known orthorombic anisotropic bubble materials. The lattice constant of the garnet film in this example is a _f =
It was 12376 Å, and distortion due to the difference in lattice constant between the film and the substrate was not a cause of anisotropy. For this reason, even when various functional patterns were formed on the garnet film by vapor deposition or sputtering, the additional strain caused by this did not interfere with the smooth movement of the bubbles. When a double conductor pattern bubble magnetic domain element was fabricated using this material, a sufficient transfer margin width was obtained. Even when this material was used in conventional devices using permalloy patterns, the yield of devices was improved because the process of suppressing hard bubbles could be omitted. In addition, no breakdown in transfer speed occurred during stripe magnetic domain transfer in the stretcher section. When this material is used as a laser beam deflection element, not only is high-speed driving possible, but the ^Faraday rotation angle is large (-
4000deg/cm) The S/N ratio of the signal has improved. When this material was used in an element that magnetically transfers information from a magnetic recording medium and reads it out using laser light, it was possible to extend the recording and reproducing frequency to 7MHz. Furthermore, since Bi ³⁺ is substituted in this material, the Faraday rotation angle can be increased, and the signal S/N ratio can be increased to over 45 dB. Example 2 Using melt composition 1 shown in Table 1, Y _1.25 was deposited on a (110) Gd ₃ Ga ₅ O ₁₂ substrate at a temperature of 824°C _.
When an epitaxial film was grown with _{a Tm 1.25 Bi 05 Fe 3.8 Ga 1.2 O 12 garnet liquid phase , it} became an orthorombic anisotropic bubble material with magnetic anisotropy perpendicular to the film surface. The magnetic properties of this LPE film are shown in Table 2. The values of Ku and △ were +1400erg/cm ³ and +10700erg/cm ³ respectively. Example 3 Y ₁ . ₄ using melt composition 1 shown in Table 1
Tm ₁ . ₄ Bi ₀ . ₂ Fe ₃ . ₉ Ga ₁ . ₁ O ₁₂ Garnet liquid phase epitaxial film was grown at 935°C on a (110) Dy ₂ . ₀ Gd ₁₀ Ga ₅ O ₁₂ substrate (lattice constant 12341 Å). As a result, Ku=
A 1 μm diameter bubble material having orthorombic anisotropy of +20,000 erg/cm ³ Δ=+11,000 erg/cm ³ was obtained. The properties of this garnet film as a bubble material were as shown in Table 2. The lattice constant of this garnet film was 12343 Å. Example 4 A cell with a lattice constant of 12335 Å
Tm ₂ . ₇ Bi ₀ . ₃ Fe ₃ . ₆₅ Ga ₁ . ₃₅ O ₁₂ Garnet liquid phase epitaxial film was prepared using (110) Dy ₂ . ₀ Gd ₁ . ₀ Ga ₅ using melt composition 2 shown in Table 1. When grown on an O ₁₂ substrate at 862℃, Ku=3000erg/cm ³ , △=+12000erg/cm ³
It has become a material with orthorombic anisotropy. The properties of this garnet film as a bubble material were as shown in Table 2. Example 5 Using melt composition 3 shown in Table 1, the lattice constant was
When a 12.370 Å Y ₂ . ₉₅ Bi ₀ . ₀₅ Fe ₃ . ₈ Ga ₁ . ₂ O ₁₂ garnet liquid phase epitaxial film was grown on a (110) Gd ₃ Ga ₅ O ₁₂ substrate at 957°C, Ku = 8900 erg. /cm ³ , △
The resulting material has orthorombic anisotropy of = -2100erg/ ^cm3 . In this case, unlike the cases of Examples 1 to 4, Δ<0, and [1
10] became the intermediate axis of magnetization. The properties of this garnet film as a bubble material were as shown in Table 2. Example 6 Using melt composition 3 shown in Table 1, the lattice constant was
When a _{Y 2} . ₅ Bi ₀ . _{5 Fe 3 . 95 Ga 1 .} ^cm3 , △
The material has an orthorombic anisotropy of =14500erg/ ^cm3 . The properties of this garnet film as a bubble material were as shown in Table 2. Example 7 Using melt composition 4 shown in Table 1, the lattice constant was
_{12417Å Y2.3Bi0.7Fe4.1Ga0.9O12 Garnet liquid phase epitaxial film ( 110 ) Gd1.5Sm1.5Ga5O12 _ _ _ _}
(Lattice constant: 12410 Å) When grown on a substrate at a temperature of 810°C, Ku = 7500erg/cm ³ , △ = 27500erg/cm ³
It has become a material with orthorombic anisotropy. The properties of this garnet film as a bubble material were as shown in Table 2. Example 8 Using melt composition 5 shown in Table 1, Y ₁ . ₄
Tm ₁ . ₄ Bi ₀ . ₂ Fe ₃ . ₉ Ga ₀ . ₁₇ Al ₀ . ₄ O ₁₂ Garnet liquid phase epitaxial film was grown at 921°C on a (110) Dy ₃ Ga ₅ O ₁₂ substrate (lattice constant 12320 Å). Then, Ku
A 1 μm diameter bubble material having orthorombic anisotropy of =+24,300 erg/cm ³ and Δ=+9,700 erg/cm ³ was obtained. The properties of this garnet film as a bubble material were as shown in Table 2. The lattice constant of this garnet film was 12322 Å. Example 9 Using melt composition 6 shown in Table 1, the lattice constant was
A Y ₂ . ₃ Bi ₀ . ₇ Fe ₄ . ₁ Al ₀ . ₉ O ₁₂ garnet liquid phase epitaxial film of 12377 Å was grown on a (110) Gd ₃ Ga ₅ O ₁₂ substrate (lattice constant 12383 Å) at a temperature of 802°C. As a result, the material had orthorombic anisotropy of Ku=+10,300 erg/cm ³ and Δ=31,400 erg/cm ³ . The characteristics of this garnet film as a bubble material are
The values were as shown in the table.

【table】

[Table] As described above, by using the present invention, when used as a bubble element material, the bubble domain wall state is S=
Only zero bubbles exist, and a bubble magnetic domain element using a double conductor pattern with a wide transfer margin can be obtained. When used as a magnetic transfer/optical readout element, an element with a wide frequency band can be obtained.
When used as a laser beam deflection element, high frequency driving becomes possible.

[Brief explanation of the drawing]

The figure shows the growth on a (110) substrate.
The relationship between the bubble movement speed and the driving magnetic field in Y ₁₃ Tm ₁ . ₃ Bi ₀ . ₄ Fe ₃ . ₇ Ga ₁ . ₃ O ₁₂ is shown.

Claims (1)

[Claims] 1 The composition formula is R ₃ Ga ₅ O ₁₂ (R is Sm, Gd or
A single crystal garnet film for magnetic and magneto-optical elements, which is formed on a non-magnetic garnet substrate represented by Dy or a combination thereof, has the same crystallographic orientation as the substrate, and has an axis of easy magnetization perpendicular to the film surface. , the film composition is (Y _1-x Tm _x ) _3-y Bi _y Fe _5-z
(Ga _1-w Al _w ) _z O ₁₂ (0≦x≦1, 0.05≦y≦
0.7, 0.9≦z≦1.35 and 0≦w≦1), and the film plane orientation is (110).