Magnetostatic wave device

Abstract: Disclosed therein is a magnetostatic wave device comprising a single-crystal thin film of iron-containing magnetic gamet, characterized in that the magnetic gamet has added therein an amount of 10 to 3000 ppm by weight of indium or tin. Input power for saturation can be very small if single-crystal thin film of YIG (as well as iron-containing magnetic gamet) for the magnetostatic wave device is added with indium in an amount of 10 to 3000 ppm (by weight). Transient response can be minimized if single-crystal thin film of YIG (as well as iron-containing magnetic gamet) for the magnetostatic wave device is added with tin in an amount of 10 to 3000 ppm (by weight).

Description: The present invention relates to a magnetostatic wave device. Background of the Invention: The magnetostatic wave device employs single-crystal thin film of magnetic garnet which has conventionally been YIG (yttrium iron garnet) represented by Y 3 Fe 5 O 12 . YIG is characterized most by its extremely small ferromagnetic half-width (ΔH). This leads to the fact that the magnetostatic wave device that employs a single-crystal thin film of magnetic garnet has only a little difference between input signals and output signals. Another feature of YIG is that it becomes saturated upon application of input signals with a comparatively small power. These characteristic properties permit a single-crystal thin film of YIG (as well as other iron-containing garnets) to be used widely for the magnetostatic wave device such as limiter and noise filter. SUMMARY OF THE INVENTION Recent electronic machines with a less power consumption than before need a new version of YIG which becomes saturated upon application of a very small input power. Accordingly, it is a first object of the present invention to provide a high-performance magnetostatic wave device which becomes saturated upon application of a very small input-power. The fact that YIG becomes saturated upon application of input signals leads to the transient response which is a phenomenon that saturation does not occur immediately after application of input signals, with input signals being outputted as such, and saturation takes place with lapse of time. This transient response adversely affects the performance of the magnetostatic wave device. Accordingly, it is a second object of the present invention to provide a high-performance magnetostatic wave device which is free from transient response (which is a phenomenon that input signals are outputted as such and saturation takes place with lapse of time). The first aspect of the present invention resides in a magnetostatic wave device comprising a single-crystal thin film of iron-containing magnetic garnet, characterized in that the magnetic garnet has added therein an amount of 10 to 3000 ppm by weight of indium. The second aspect of the present invention resides in a magnetostatic wave device comprising a single-crystal thin film of iron-containing magnetic garnet, characterized in that the magnetic garnet has added therein an amount of 10 to 3000 ppm by weight of tin. It turned out that input power for saturation can be very small if single-crystal thin film of YIG (as well as iron-containing magnetic garnet) for the magnetostatic wave device is added with indium in an amount of 10 to 3000 ppm (by weight). It also turned out that transient response can be minimized if single-crystal thin film of YIG (as well as iron-containing magnetic garnet) for the magnetostatic wave device is added with tin in an amount of 10 to 3000 ppm (by weight). The first aspect of the present invention is designed to make best use of YlG's capability of becoming saturated upon application of a very small input power, thereby providing a high-performance magnetostatic wave device. The second aspect of the present invention makes best use of YIG's feature that saturation takes place without delay upon application of input signals of small power. This makes it possible to minimize transient response, thereby enhancing the performance of the magnetostatic wave device. These and other objects, advantages, and features of the invention may be readily ascertained by referring to the accompanying drawing and the following detailed description of embodiments and examples. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing one embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a perspective view showing one embodiment of the present invention, which is a magnetostatic wave device 10. It is composed of a rectangular substrate 12 of Gd 3 Ga 5 O 12 and a rectangular single-crystal thin film 14 of magnetic garnet formed on one surface thereof. (The magnetic garnet contains iron.) On the surface of the single-crystal thin film 14 of magnetic garnet are placed an input terminal 16 and an output terminal 18 which are parallel to each other. These terminals have their ends grounded. The magnetic garnet has a composition represented by (Y 3-x1- x2 R' x1 R'' x2 )(Fe 5-y1-y2 M' y1 M'' y2 )O 12 , wherein 0 ≤ x1 ≤ 3, 0 ≤ x2 ≤ 3, 0 ≤ x1+x2 ≤ 3, 0 ≤ y1 < 5, 0 ≤ y2 3, 0 ≤ y1+y2 < 5, and x2=y2; R' is at least one member selected from Sc, Bi, and La series; R" is at least one member selected from Mg, Ca, Sr, and Ba; M' is at least one member selected from Al, Ga, and In; and M" is at least one member selected from Si, Ti, Zr, Hf, and Ge. The first aspect of the present invention is demonstrated by Examples 1 to 3, and the second aspect of the present invention is demonstrated by Examples 4 to 6. Example 1 A garnet thin film was formed by liquid phase epitaxy (LPE) on a GGG substrate (gadolinium gallium garnet represented by Gd 3 Ga 5 O 12 ) in the following manner. First, Fe 2 O 3 and Y 2 O 3 as the raw materials of garnet were mixed with InO 2 as an additive and PbO-B 2 O 3 as a flux. Then the mixture was placed in a platinum crucible held in a vertical electric furnace and then melted and homogenized at about 1200 °C. The melt was cooled to and kept at about 900 °C so that garnet became supersaturated. Into this melt was dipped the GGG substrate, which was rotated for a prescribed period of time for crystal growth. Finally, the substrate was raised from the melt and then spun rapidly to remove the excess melt by centrifugal force. Thus there was obtained the desired garnet thin film. For comparison, the same procedure as above was repeated without the addition of indium. The thus obtained garnet thin film was fabricated into the magnetostatic wave device as shown in Fig. 1. The device was measured for the amount of input power (at 2 GHz) required for the device to become saturated. Also, the garnet film underwent chemical analysis to determine the content of indium. The results are shown in Table 1. Sample No. Composition Content of indium in garnet thin film (ppm by weight) Amount of input power for saturation (mW) 1 Y 3 Fe 5 O 12 0 3.2 2 Y 3 Fe 5 O 12 5 3.0 3 Y 3 Fe 5 O 12 10 1.5 4 Y 3 Fe 5 O 12 500 1.3 5 Y 3 Fe 5 O 12 1000 1.2 6 Y 3 Fe 5 O 12 1500 1.0 7 Y 3 Fe 5 O 12 3000 0.9 8 Y 3 Fe 5 O 12 3100 - According to the present invention, the content of indium in the garnet is specified as above because a content less than 10 ppm (by weight) is not enough to effectively contribute to saturation (as in Sample No. 2 which is similar to Sample No. 1 containing no indium) and a content in excess of 3000 ppm (by weight) is unfavorable to the formation of good single-crystal thin film (as in Sample No. 8). Example 2 A garnet thin film was formed by LPE on a GGG substrate (Gd 3 Ga 5 O 12 ) in the following manner. First, Fe 2 O 3 , Y 2 O 3 , Ga 2 O 3 , and La 2 O 3 as the raw materials of garnet were mixed with InO 2 as an additive and PbO-B 2 O 3 as a flux. Then the mixture was placed in a platinum crucible held in a vertical electric furnace and then melted and homogenized at about 1200 °C. The melt was cooled to and kept at about 900 °C so that garnet became supersaturated. Into this melt was dipped the GGG substrate, which was rotated for a prescribed period of time for crystal growth. Finally, the substrate was raised from the melt and then spun rapidly to remove the excess melt by centrifugal force. Thus there was obtained the desired garnet thin film. For comparison, the same procedure as above was repeated without the addition of indium. The thus obtained garnet thin film was fabricated into the magnetostatic wave device as shown in Fig. 1. The device was measured for the amount of input power (at 2 GHz) required for the device to become saturated. Also, the garnet film underwent chemical analysis to determine the content of indium. The results are shown in Table 2. Sample No. Composition Content of indium in garnet thin film (ppm by weight) Amount of input power for saturation (mW) 9 Y 2.96 La 0.04 Fe 4.6 Ga 0.4 O 12 0 2.9 10 Y 2.96 La 0.04 Fe 4.6 Ga 0.4 O 12 5 2.8 11 Y 2.96 La 0.04 Fe 4.6 Ga 0.4 O 12 10 1.4 12 Y 2.96 La 0.04 Fe 4.6 Ga 0.4 O 12 500 1.3 13 Y 2.96 La 0.04 Fe 4.6 Ga 0.4 O 12 1000 1.2 14 Y 2.96 La 0.04 Fe 4.6 Ga 0.4 O 12 1500 1.0 15 Y 2.96 La 0.04 Fe 4.6 Ga 0.4 O 12 3000 0.9 16 Y 2.96 La 0.04 Fe 4.6 Ga 0.4 O 12 3100 - According to the present invention, the content of indium in the garnet is specified as above because a content less than 10 ppm (by weight) is not enough to effectively contribute to saturation (as in Sample No. 10 which is similar to Sample No. 9 containing no indium) and a content in excess of 3000 ppm (by weight) is unfavorable to the formation of good single-crystal thin film (as in Sample No. 16). Example 3 A garnet thin film was formed by LPE on a GGG substrate (Gd 3 Ga 5 O 12 ) in the following manner. First, Fe 2 O 3 , Y 2 O 3 , Ga 2 O 3 , and Bi 2 O 3 as the raw materials of garnet were mixed with InO 2 as an additive and PbO-B 2 O 3 as a flux. Then the mixture was placed in a platinum crucible held in a vertical electric furnace and then melted and homogenized at about 1200 °C. The melt was cooled to and kept at about 900 °C so that garnet became supersaturated. Into this melt was dipped the GGG substrate, which was rotated for a prescribed period of time for crystal growth. Finally, the substrate was raised from the melt and then spun rapidly to remove the excess melt by centrifugal force. Thus there was obtained the desired garnet thin film. For comparison, the same procedure as above was repeated without the addition of indium. The thus obtained garnet thin film was fabricated into the magnetostatic wave device as shown in Fig. 1. The device was measured for the amount of input power (at 2 GHz) required for the device to become saturated. Also, the garnet film underwent chemical analysis to determine the content of indium. The results are shown in Table 3. Sample No. Composition Content of indium in garnet thin film (ppm by weight) Amount of input power for saturation (mW) 17 Y 2.8 Bi 0.2 Fe 4.55 Ga 0.45 O 12 0 3.0 18 Y 2.8 Bi 0.2 Fe 4.55 Ga 0.45 O 12 5 2.8 19 Y 2.8 Bi 0.2 Fe 4.55 Ga 0.45 O 12 10 1.4 20 Y 2.8 Bi 0.2 Fe 4.55 Ga 0.45 O 12 500 1.3 21 Y 2.8 Bi 0.2 Fe 4.55 Ga 0.45 O 12 1000 1.2 22 Y 2.8 Bi 0.2 Fe 4.55 Ga 0.45 O 12 1500 1.1 23 Y 2.8 Bi 0.2 Fe 4.55 Ga 0.45 O 12 3000 1.0 24 Y 2.8 Bi 0.2 Fe 4.55 Ga 0.45 O 12 3100 - According to the present invention, the content of indium in the garnet is specified as above because a content less than 10 ppm (by weight) is not enough to effectively contribute to saturation (as in Sample No. 18 which is similar to Sample No. 17 containing no indium) and a content in excess of 3000 ppm (by weight) is unfavorable to the formation of good single-crystal thin film (as in Sample No. 24). Example 4 A garnet thin film was formed by liquid phase epitaxy (LPE) on a GGG substrate (gadolinium gallium garnet represented by Gd 3 Ga 5 O 12 ) in the following manner. First, Fe 2 O 3 and Y 2 O 3 as the raw materials of garnet were mixed with SnO 2 as an additive and PbO-B 2 O 3 as a flux. Then the mixture was placed in a platinum crucible held in a vertical electric furnace and then melted and homogenized at about 1200 °C. The melt was cooled to and kept at about 900 °C so that garnet became supersaturated. Into this melt was dipped the GGG substrate, which was rotated for a prescribed period of time for crystal growth. Finally, the substrate was raised from the melt and then spun rapidly to remove the excess melt by centrifugal force. Thus there was obtained the desired garnet thin film. For comparison, the same procedure as above was repeated without the addition of tin. The thus obtained garnet thin film was fabricated into the magnetostatic wave device as shown in Fig. 1. The device was measured for time required for saturation to take place (at 2 GHz). Also, the garnet film underwent chemical analysis to determine the content of tin. The results are shown in Table 4. Sample No. Composition Content of tin in garnet thin film (ppm by weight) Time required for saturation to take place (ms) 1 Y 3 Fe 5 O 12 0 124 2 Y 3 Fe 5 O 12 5 123 3 Y 3 Fe 5 O 12 10 80 4 Y 3 Fe 5 O 12 500 68 5 Y 3 Fe 5 O 12 1000 61 6 Y 3 Fe 5 O 12 1500 55 7 Y 3 Fe 5 O 12 3000 48 8 Y 3 Fe 5 O 12 3100 - According to the present invention, the content of tin in the garnet is specified as above because a content less than 10 ppm (by weight) is not enough to affect the time required for saturation to take place (as in Sample No. 2 which is similar to Sample No. 1 (YIG film) containing no tin) and a content in excess of 3000 ppm (by weight) prevents saturation itself (as in Sample No. 8), making the magnetostatic wave device inoperable. Example 5 A garnet thin film was formed by LPE on a GGG substrate (Gd 3 Ga 5 O 12 ) in the following manner. First, Fe 2 O 3 , Y 2 O 3 , Ga 2 O 3 , and La 2 O 3 as the raw materials of garnet were mixed with SnO 2 as an additive and PbO-B 2 O 3 as a flux. Then the mixture was placed in a platinum crucible held in a vertical electric furnace and then melted and homogenized at about 1200 °C. The melt was cooled to and kept at about 900 °C so that garnet became supersaturated. Into this melt was dipped the GGG substrate, which was rotated for a prescribed period of time for crystal growth. Finally, the substrate was raised from the melt and then spun rapidly to remove the excess melt by centrifugal force. Thus there was obtained the desired garnet thin film. For comparison, the same procedure as above was repeated without the addition of tin. The thus obtained garnet thin film was fabricated into the magnetostatic wave device as shown in Fig. 1. The device was measured for time required for saturation to take place (at 2 GHz). Also, the garnet film underwent chemical analysis to determine the content of tin. The results are shown in Table 5. Sample No. Composition Content of tin in garnet thin film (ppm by weight) Time required for saturation to take place (ns) 9 Y 2.95 La 0.05 Fe 4.6 Ga 0.4 O 12 0 122 10 Y 2.95 La 0.05 Fe 4.6 Ga 0.4 O 12 5 121 11 Y 2.95 La 0.05 Fe 4.6 Ga 0.4 O 12 10 78 12 Y 2.95 La 0.05 Fe 4.6 Ga 0.4 O 12 500 70 13 Y 2.95 La 0.05 Fe 4.6 Ga 0.4 O 12 1000 60 14 Y 2.95 La 0.05 Fe 4.6 Ga 0.4 O 12 1500 54 15 Y 2.95 La 0.05 Fe 4.6 Ga 0.4 O 12 3000 49 16 Y 2.95 La 0.05 Fe 4.6 Ga 0.4 O 12 3100 - According to the present invention, the content of tin in the garnet is specified as above because a content less than 10 ppm (by weight) is not enough to affect the time required for saturation to take place (as in Sample No. 10 which is similar to Sample No. 9 containing no tin) and a content in excess of 3000 ppm (by weight) prevents saturation itself (as in Sample No. 16), making the magnetostatic wave device inoperable. Example 6 A garnet thin film was formed by LPE on a GGG substrate (Gd 3 Ga 5 O 12 ) in the following manner. First, Fe 2 O 3 , Y 2 O 3 , Ga 2 O 3 , and Bi 2 O 3 as the raw materials of garnet were mixed with SnO 2 as an additive and PbO-B 2 O 3 as a flux. Then the mixture was placed in a platinum crucible held in a vertical electric furnace and then melted and homogenized at about 1200 °C. The melt was cooled to and kept at about 900 °C so that garnet became supersaturated. Into this melt was dipped the GGG substrate, which was rotated for a prescribed period of time for crystal growth. Finally, the substrate was raised from the melt and then spun rapidly to remove the excess melt by centrifugal force. Thus there was obtained the desired garnet thin film. For comparison, the same procedure as above was repeated without the addition of tin. The thus obtained garnet thin film was fabricated into the magnetostatic wave device as shown in Fig. 1. The device was measured for time required for saturation to take place (at 2 GHz). Also, the garnet film underwent chemical analysis to determine the content of tin. The results are shown in Table 6. Sample No. Composition Content of tin in garnet thin film (ppm by weight) Time required for saturation to take place (ns) 17 Y 2.8 Bi 0.2 Fe 4.6 Ga 0.4 O 12 0 125 18 Y 2.8 Bi 0.2 Fe 4.6 Ga 0.4 O 12 5 122 19 Y 2.8 Bi 0.2 Fe 4.6 Ga 0.4 O 12 10 79 20 Y 2.8 Bi 0.2 Fe 4.6 Ga 0.4 O 12 500 70 21 Y 2.8 Bi 0.2 Fe 4.6 Ga 0.4 O 12 1000 56 22 Y 2.8 Bi 0.2 Fe 4.6 Ga 0.4 O 12 1500 50 23 Y 2.8 Bi 0.2 Fe 4.6 Ga 0.4 O 12 3000 46 24 Y 2.8 Bi 0.2 Fe 4.6 Ga 0.4 O 12 3100 - According to the present invention, the content of tin in the garnet is specified as above because a content less than 10 ppm (by weight) is not enough to affect the time required for saturation to take place (as in Sample No. 18 which is similar to Sample No. 17 containing no tin) and a content in excess of 3000 ppm (by weight) prevents saturation itself (as in Sample No. 24), making the magnetostatic wave device inoperable.

Claims: A magnetostatic wave device comprising a single-crystal thin film of iron-containing magnetic garnet, characterized in that the magnetic garnet has added therein an amount of 10 to 3000 ppm by weight of indium. The magnetostatic wave device of Claim 1 containing indium in an amount of at least 500 ppm. The magnetostatic wave device of Claim 2 containing indium in an amount of at least 1000 ppm.

Inventors: FUJINO MASARU, FUJINO, MASARU
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1997
Main classification: H03H2
IPC codes: H01F10, H03H2, H01F41