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The authors are investigating the possibility of using bulk magnets in the Maglev system. It is considered that bulk magnets for the Maglev system must be composed of numerous superconducting bulks arranged in rows and columns for each magnet pole because a bulk superconductor with a high critical current density doesn't have a sufficiently large size for Maglev magnet. Therefore, it is necessary to examine the flux-trapping characteristic of superconducting bulks arranged in array. Flux-trapping experiments are performed using the melt-processed YBaCuO superconducting bulks arranged in rows and columns, in which each bulk individually has a magnetizing coil, and the bulks are magnetized by field cooling. It is found that, when the superconducting bulks are arranged in rows and columns, the trapped flux density and the generated magnetic field are smaller than those when a superconducting bulk is used alone. The rate of decreases in the trapped flux density and the generated magnetic field becomes larger with increases in the number of superconducting bulks arranged in array. The trapped flux decreases conspicuously in particular at a superconducting bulk surrounded by other superconducting bulks.

One of the applications of a bulk magnet in which flux is trapped in oxide superconducting bulks is a superconducting magnet for Maglev systems. We are investigating the possibility of using bulk magnets in Maglev systems. It is believed that bulk magnets far Maglev systems must be composed of superconducting bulks arranged in rows and columns for every pole, because a superconductor made of melt-processed Y-Ba-Cu-O with a high critical current density is smaller in size than the pole. Therefore, it is necessary to examine the flux-trapping characteristics of superconducting bulks in an array. Flux-trapping experiments are performed using melt-processed Y-Ba-Cu-O superconducting bulks arranged in rows and columns, in which each bulk has a magnetizing coil (an individual magnetization method) or all bulks have one magnetizing coil centered at outer bulks in an array (unified magnetization method), and the bulks are magnetized by field cooling. The magnetic field on the superconducting bulks arranged in an array is smaller than that of the single bulk arrangement because the magnetic field generated by the surrounding superconducting bulks acts to weaken the field of the surrounded suerconducting bulk. Furthermore, in the case of the individual magnetization method, the magnetic field applied is decreased during field cooling so that the trapped flux is smaller too. The rate of decrease in the individual magnetization method is larger than the rate of decrease in the unified magnetization method. It is clear that the unified magnetization method is more suitable than individual magnetization for magnetizing bulk magnets for aglev systems, which require a high magnetic field and large-scale system.

Strong magnetic fields can be generated for magnetization of the high-Tc superconductor (HTS) with pulsed magnetic fields using a small exciting coil. In the present study, magnetization using the pulsed magnetic field is performed on HTS bulk samples in the zero-field cooled state. In order to saturate the magnetization, it was necessary to optimize the time constant of the magnetic flux invasion and the flux flow during the increasing and decreasing processes of the pulsed magnetic field. Therefore, we measured the magnetic flux density on the pulsed field magnetization process and explained the relation between the pulsed magnetic field and the time constant of the magnetic flux invasion and flux flow. An empirical model of the pulsed field magnetization process was also proposed and optimum conditions were studied for pulsed field magnetization of the HTS. From this study, it was confirmed that an optimum pulsed waveform existed for pulsed field magnetization.

A method of manufacturing potassium niobate single crystal thin film on a single crystal substrate that epitaxially grows orthorhombic potassium niobate single crystal at a temperature near room temperature at a high deposition rate. A surface acoustic wave element, frequency filter, frequency oscillator, electronics circuit, and electronic device employ the thin film manufactured by the method, and are high in k 2 , wideband, downsized, and economical in power consumption. The method includes the steps of coating liquid drops of a potassium niobate solution on a SrTiO 3 single crystal substrate by a liquid drop emission method, and precipitating potassium niobate single crystal layer by epitaxial growth from the liquid drops.

A surface acoustic wave element includes a single crystal substrate; a buffer layer formed by a crystal film that is formed on top of the single crystal substrate; and a piezoelectric thin film having a hexagonal system or a trigonal system crystal structure that is formed on top of the buffer layer. The surface acoustic wave element has an improved performance by improving the film quality of the piezoelectric thin film. In addition, because a semiconductor device can be formed on the single crystal substrate, the surface acoustic wave element can be integrated with the semiconductor device. Moreover, leakages of surface acoustic waves into the single crystal substrate are prevented. There are also provided a frequency filter, an oscillator, an electronic circuit, and an electronic instrument that are provided with this surface acoustic wave element.