Anisotropic low-field magnetization of heavy-fermion superconductor URu2Si2

Using a sensitive Hall-probe technique, the magnetization anisotropy of the heavy-fermion superconductor URu₂Si₂ , with T_c=1.2 K, was studied as a function of magnetic field and temperature on a cube-shaped sample. The estimated first-critical-field values, H_c1, extrapolated to T=0 are about 10 and 15 Oe for field parallel to the a- and c-crystallographic directions, respectively. The low-field critical-current density, J_c, exhibits a similar anisotropy as H_c1 but J_c is suppressed in particular by magnetic field oriented along the c-direction. It is argued that results of magnetization measurements should depend on the sample size and shape