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.