Rare-Earth-Dependent Tri-axial Magnetic Anisotropies and Growth Conditions in REBa2Cu4O8

Tri-axial orientation under modulated rotation magnetic fields (MRFs) and the growth of single crystals in ambient pressure were demonstrated in various REBa2Cu4O8 (RE124; RE, rare earth elements) compounds. RE124 crystals have been successfully grown for RE = Y, Sm, Eu, Gd, Dy, Ho, and Er. Optimal growth temperature regions for RE124 largely depended on the type of RE and became narrower in the case of lighter RE ions. By applying an MRF of 10 T, powders of all the grown RE124 were tri-axially oriented in epoxy resin at room temperature, and their orientation axes were clearly dependent on the type of RE ions in RE124. Furthermore, it was found from the changes in the degree of orientation under three different MRF conditions that tri-axial single-ion magnetic anisotropies of heavy RE3+ ions were highest among magnetic anisotropies generated by Cu-O networks and RE3+ ions. The appropriate choice of RE ions in RE-based cuprate superconductors enables the reduction of the magnetic field required for the production of bulk and thick films based on the magnetic orientation technique. (C) 2012 The Japan Society of Applied Physics