Superconducting and normal-state magnetic-susceptibility anisotropy in YBa2Cu3O7

Abstract

Measurements of the superconducting and normal-state magnetic-susceptibility χ anisotropies of high-purity grain-aligned powder samples of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ are reported. Excellent alignment was achieved using a noncontaminating in situ technique. We find a strong temperature-dependent anisotropy Δχ==${\chi }_c$-${\chi }_{\mathrm{ab}}$ that decreases from positive values for T>$T_c$ to negative values for T<$T_c$, consistent with reported torque-magnetometer measurements on single crystals. Estimates of the normal-state spin contributions to χ are obtained and compared with previous results.