Elucidation of Crystal-Chemical Determination Factor of Magnetic Anisotropy in HTSC

Easy axes of magnetization at room temperature in REBa 2 Cu 3 O y (RE: rare earth) and Bi 2 Sr 2 Ca 1-x RE x Cu 2 O y were clarified using their powders oriented in a static magnetic field. The easy axes clearly depended on the type of RE which could be mainly explained in terms of second-order Stevens factors and magnetic anisotropy of the CuO 2 plane. Furthermore, we found the difference in magnetic effects of Er 3+ for orientation through systematic evaluations of Er-doped Y123 and Bi2212 powders. This result means that magnetic anisotropies of RE 3+ ions are sensitive to not only the type of RE but also local structure of oxygen ions surrounding RE 3+ ions.