JPS6129128B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to materials for magnetic and magneto-optical elements such as bubble magnetic domain elements, laser beam polarizing elements, and optical isolators using garnet epitaxial films, and in particular to materials for magnetic and magneto-optical elements such as bubble domain elements, laser beam polarizing elements, and optical isolators, using garnet epitaxial films.
It relates to a material in which Ca and Bi are simultaneously substituted and Ge, Si, or a combination thereof is substituted at the 24d position. In a bubble magnetic domain element, as the bubble diameter becomes smaller, the value of the uniaxial anisotropy energy Ku perpendicular to the film surface required to maintain the bubble magnetic domain increases. If we assume that the magnitude of the Q factor, which indicates the stability of the bubble, and the value of the exchange constant A are constant, then this relationship can be established as follows from The Bell System Technical Journal.
As shown in Vol. 50, page 725 (1971), it is inversely proportional to the square of the bubble diameter d (Equation (1)). Ku=256AQ ² /d ² (1) This shows that if the bubble diameter d is kept constant, if Q is to be increased, Ku must be increased. On the other hand, the operating frequency of the element is related to the domain wall mobility μ _w of the material. The relationship between μ _w and Ku is described in AIP Conference Proceedings, No. 5.
As shown on page 72 of the issue (1971), μ _w is inversely proportional to the product of Ku to the 1/2 power and the damping coefficient α. Here |γ| is the gyromagnetic ratio. The isomer energy Ku of the bubble material is mainly due to the growth-induced magnetic anisotropy, and increasing it is generally achieved by increasing the content of magnetic rare earth ions such as Sm and Eu in the garnet. However, this means increasing the damping coefficient of the garnet. Therefore, increasing the stability of the bubble and ensuring high speed are mutually necessary requirements. It is important to solve this problem when developing microbubble materials. If the braking coefficient α is not increased
If Ku can be increased, a material that is highly stable and capable of high-speed operation can be achieved. Figure 1 shows 1. (YSmLuCa) ₃ (FeGe) ₅ O ₁₂ , 2.
(YSmTm) ₃ (FeGa) ₅ O ₁₂ and 3 (YEuTm) ₃
(FeGa) ₅ O ₁₂ The anisotropic energy values in the garnet epitaxial film are Sm and Lu, respectively.
These are the results of experiments investigated as a function of each rare earth ion pair of Sm and Tm and Eu and Tm. This means that
This shows that in order to obtain the desired magnitude of anisotropic energy, it is sufficient to generate the necessary amount of rare earth ion pairs in the film. What should be noted here is that the amount of ion pairs represented by [A] and [B] is important, and the content of the A and B type ions itself is not a problem. When using Sm and Lu ion pairs to obtain the amount of ion pairs [Sm] and [Lu] necessary to produce the desired growth-induced magnetic anisotropy, if a large amount of Sm ions is used, Due to the magnitude of the damping coefficient α, the mobility μ _w of the obtained garnet film becomes small. However, when increasing the number of Lu ions to obtain an equal amount of ion pairs [Sm] and [Lu], the amount of Sm ions with large α can be reduced, and since Lu ions are nonmagnetic ions, the garnet film Mobility μ _w increases. On the other hand, when a garnet film is epitaxially grown on a gadolinium gallium garnet substrate with a lattice constant of 12.383 Å, the crystallinity of the epitaxial film is improved by keeping the lattice constant mismatch between the substrate and the film within 0.1%. It is important to keep the
Therefore, the small ionic radius in garnet
In order to increase the content of Lu ions (0.97 Å), it is important to replace the necessary amount of ions with a large ionic radius. Moreover, if this ion is not magnetic, it has no meaning from the purpose of increasing the value of μ _w . Furthermore, when the bubble diameter is miniaturized, there is a problem in that the garnet film thickness decreases. Since the bubble diameter and the film thickness are approximately equal, the film thickness is approximately 2 μm for a 2 μm diameter bubble material and approximately 1 μm for a 1 μm diameter bubble material. When the film thickness is 2 μm or less, it becomes quite difficult to observe bubble magnetic domains due to the Faraday effect. It is known that the Faraday rotation ability of garnet can be improved by substituting Bi ions. In addition, in order to match the temperature coefficient of magnetization of barium ferrite for generating a bias magnetic field, which is necessary when constructing a bubble element, and the temperature coefficient of the bubble extinguishing magnetic field, some of the Fe ions at the 24d position must be replaced with tetravalent Ge. It is important to use a Ca-Ge based garnet in which an equal amount of Ca is substituted at the 24C position in order to maintain electrical neutrality by substitution with Ge ions. In addition, a laser beam deflection element that uses striped magnetic domains generated in bubble magnetic domain element material as an optical diffraction grating using the Kerr effect or Faraday effect requires a garnet film with a large Faraday rotation angle and a high frequency to increase the deflection frequency. Mobility materials are desirable. Furthermore, in the field of 1.3 μm optical fiber communication, which has seen remarkable technological progress in recent years, in order to prevent the light source itself from becoming unstable due to the reflected light of the light source laser light, the Institute of Electronics and Communication Engineers General National Conference 1981: Lecture No. S3 -3, an optical isolator is required. Currently, the materials are
Although YIG single crystal is used, it is important to make it thinner in order to make the device more compact and increase reliability. For this reason as well, a garnet epitaxial film with a large Faraday rotation angle is required.
Furthermore, in order to reduce absorption loss during light propagation, it is important to minimize the amount of Pb ²⁺ or Pt ⁴⁺ mixed in from the growth melt or partially melted crucible material during garnet growth. This makes it possible to increase the figure-off benefit, which is the ratio between the Farad day rotation coefficient and the amount of absorption. The present inventor has completed the present invention by paying attention to the above-mentioned matters. In other words, by substituting Ca ions and Bi ions with a large ionic radius (1.11 Å) and a large absolute value of Faraday rotation ability at the 24C position of rare earth garnet, and by substituting Ge ions at the 24d position, high temperature can be achieved over a wide temperature range. A material for magnetic and magneto-optical elements such as a bubble magnetic domain element, a laser beam deflection element, and an optical isolator element, which can guarantee stable and high-speed operation and has a large absolute value of Faraday rotation angle, can be obtained. A detailed explanation will be given below using examples. Example 1 Bi ₀ . _{460 Lu 1} . ₄₇₆ Sm ₀ . ₃₆₄ Ca ₀ . ₇ Fe _{4 . 3 Ge} 0 . When grown on a (111)Gd ₃ Ga ₅ O ₁₂ substrate, it exhibited magnetic properties as shown in Table 2. In other words, this garnet film with a bubble diameter of 1.6 μm has a high mobility of 500 KHz.
Sufficient transfer margin can be secured even during high-speed operation of
Guaranteed within the range of ℃. This characteristic is _similar to that of the conventional Ca, Ge substituted garnet _Y0.504 shown in Comparative Example 1.
Compared to Sm _{0.560 Lu 1.175} Ca _{0.761 Fe 4.239 Ge 0.761 O 12 ,}
It was excellent in terms of dynamic mobility. In addition, in Example 1, Bi is substituted at the same 24C position.
_{Temperature characteristics ( temperature coefficient of bubble} extinguishing _{magnetic field} ) is excellent. The temperature coefficient of _the bubble extinguishing magnetic _field of Y ₂ . ₄ Bi ₀ . ₆ Fe _{4 . 2} Ga ⁰ . Nakatsuta. Example ₂ Bi _{0.60 Lu 1.45} Sm _0.40 Ca _0.55 Fe _{4.45 Ge 0.55} O ₁₂ Garnet liquid phase epitaxial film ( ₁₁₁ )Gd _{3 Ga 5 O 12}
When grown on a substrate, a submicron bubble material with a domain diameter of 0.60 μm as shown in Table 2 was obtained, and excellent high frequency drive characteristics and temperature characteristics were obtained. Moreover, this material has a film thickness of 0.41
Despite being as thin as μm, it was possible to observe the bubble magnetic domain using an ordinary polarizing microscope.
However, it does not contain Bi ions as shown in Comparative Example 3.
In the case _{of Sm 0.75 Lu 1.75 Ca 0.5 Fe 4.5 Ge 0.5 O 12 garnet epitaxial} film, bubble magnetic domains can be visually observed even though the film thickness is _{1.07 μm} . That was impossible. Therefore, the magnetic properties shown in Comparative Example 3 are estimated values from properties measured by other means except for the film thickness. Example 3 Y ions were added to the film composition of Example 1.
_{Bi 0.30 Y 0.50 Lu 1.22 Sm 0.23 Ca 0.75 Fe 4.25 Ge 0.75 O 12 garnet liquid phase epitaxial} film (111),
When grown on a Gd ₃ Ga ₅ O ₁₂ substrate, the value of the Q factor was slightly smaller than the characteristics of Example 1, but the value of the temperature coefficient of mobility and bubble extinguishing magnetic field was improved compared to Example 1. Example ₄ Bi _0.15 Eu _0.432 Tm _{1.748 Ga 0.67 Fe 4.33 Ge 0.67} O ₁₂ Garnet liquid _phase epitaxial film (111)
When grown on a Gd ₃ Ga ₅ O ₁₂ substrate, the magnetic properties shown in Table 2 were obtained. With this material, the visibility of bubble domains is slightly improved compared to conventionally known materials that do not contain Bi ions, and the lower limit of the amount of Bi ion substitution required to make bubble domains easier to observe is garnet. It was found to be 0.15 per molecular formula. _{Example 5} Eu _1.985 La _{0.795 Bi 0.20} Ca _{0.02 Fe 4.23 Ge 0.02 Al 0.75 O 12}
(110) from the melt with the composition shown in Table 3.
A garnet film having orthorombic anisotropy grown on a Nd ₃ Ga ₅ O ₁₂ substrate by liquid phase epitaxial growth exhibited magnetic properties as shown in Table 2.
By replacing Bi ions, the difficulty in observing the bubble magnetic domain due to the pale purple coloring of the Nd ₃ Ga ₅ O ₁₂ substrate was eliminated, and the movement of the bubble magnetic domain could be easily measured visually. Of course, the substitution effect of Bi ions does not depend on the type and orientation of the substrate crystal. Example 6 By epitaxially growing a Bi ₀ . ₆₅ Lu ₁ . ₇₅ Ca ₀ . ₆ Fe ₄ . ₄ Ge ₀ . ₆ O ₁₂ garnet film from a melt similar to that in Example 1, a large Faraday rotation angle was obtained. A material for a laser beam deflection device was obtained. This material does not contain ions with a large damping coefficient α, so
Laser scanning at 5MHz was possible. Example 7 _{When a Y2.38Bi0.6Ca0.02Fe4.98Ge0.02O12 garnet} liquid _phase epitaxial film was grown _{on a ( 100 ) Gd3Ga5O12 substrate , a} A material for optical isolator elements with a large rotation angle was obtained. The same was true when using (111) and (110) substrates. By introducing a small amount of Ca and Ge ions into the garnet, they can be taken into the garnet from the growing melt, which is a problem with conventional garnets that are composed only of trivalent ions and do not contain Ca or Ge ions. Pb ²⁺ or
Uncompensated Fe ⁴⁺ or Fe ²⁺ produced by Pt ⁴⁺
It has the effect of compensating for light absorption, reducing light absorption, and increasing the figure of merit. As a result, an optical isolator with low optical propagation loss could be obtained. Example 8 Y ₂ . ₁ Bi ₀ . ₈ Ca ₀ . ₁ Fe ₄ . ₉ Ge ₀ . ₀₅ Si ₀ . ₀₅ O ₁₂ Garnet thin film was made by high frequency sputtering method (111)
When grown to Gd ₃ Ga ₅ O ₁₂ , an optical isolator material with a large figure of merit was obtained. As explained above, by using the present invention, it is possible to obtain a bubble magnetic domain element material that guarantees high stability and high-speed operation over a wide temperature range, and also allows easy visual observation of bubble magnetic domains. Magnetic and magneto-optical element materials such as deflection element materials and isolator materials with low optical propagation loss are obtained.

【table】

【table】

【table】 [Brief explanation of the drawing]

The figure shows the uniaxial magnetic anisotropy energy as a function of ion pairs in garnet, where 1 is (YSmLuCa) ₃ (FeGe) ₅ O ₁₂ and 2 is (YSmTm).
(FeGa) ₅ O ₁₂ , 3 represents (YEuTm) ₃ (FeGa) ₅ O ₁₂ .

Claims (1)

[Claims] 1 The general formula is Ln _3-xy Bi _x Ca _y Fe _5-yz A _y B _z O ₁₂ (Ln is Y, La, Ce, Pr, Nd, Sm, Eu,
A combination of one or more elements selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, where A is Ge, Si or a combination thereof, and B is Al, Ge or a combination thereof. combination), and the composition range is 0.15x0.6, 0.02y1.0,
A material for magnetic and magneto-optical elements, characterized by comprising a garnet single crystal thin film of 0z0.8.