Magnetic and structural properties of the high-T_c superconductor Ho-Ba-Cu oxide

The title material is found to have the crystal structure same as another superconductor, Y-Ba-Cu oxide. The lattice has the face-centered tetragonal symmetry and the unit cell, whose parameters are a=b=7.81±0.02 Å and c=7.665±0.02 Å, contains eight units of the perovskite structure. The magnetic susceptibility obeys essentially the Curie-Weiss formula when sufficient fields are applied. For the fields less than 200 Oe the Meissner effect is observed up to about 70 K above which a finite resistance is found. The diamagnetic susceptibility at 4.4 K reaches about 50% of a perfect diamagnetism.