Anisotropic low-field magnetization of heavy-fermion superconductor URu/sub 2/Si/sub 2/

Using a sensitive Hall-probe technique, the magnetization anisotropy of the heavy-fermion superconductor URu/sub 2/Si/sub 2/, with T/sub 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/sub 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/sub c/, exhibits a similar anisotropy as H/sub c1/ but J/sub 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.<
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