Bi-2212の一方向溶融凝固過程に対する磁場効果 : 磁性体物理

概要

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The effect of a magnetic field on the unidirectional solidification process of the high- Tc superconductor Bi_2Sr_2CaCu_2O_y (Bi-2212) was studied. The apparatus used in this study was a high-frequency heating furnace located in the room-temperature bore of a superconducting magnet. A sintered rod of Bi-2212 was put into an alumina tube, then moved parallel to the applied magnetic field direction through the high-frequency coil. The magnetic field intensity was about 7 T in the molten zone. After solidification, the initial and later parts of the samples thus obtained were cut into blocks, and X-ray diffraction and magnetization measurements were performed to evaluate their orientations. When a conventional unidirectional solidification process such as the floating-zone method is used, Bi-2212 crystals tend to grow with their caxes perpendicular to the direction of motion. On the other hand, when a high magnetic field is applied during the solidification process, samples with their caxes parallel to the direction of motion were obtained. This phenomenon was due to the paramagnetic anisotropy of Bi-2212 crystals. It can be said therefore that a magnetic field can be used to control the grain orientations in melt-solidification processes of even feeble magnetic substances.
社団法人日本磁気学会の論文
2002-04-01