Magnetic and magnetoelastic properties of GdNi: Single-crystal study

A GdNi single crystal has been prepared by the Czochralski method and studied by measuring the magnetization, electrical resistivity and thermal expansion. The ferromagnetic ordering below T C=69 K has been confirmed. The saturated magnetization at 2 K was found to be identical (7.2 μ B/f.u.) along all the three principal crystallographic directions. This result is in agreement with theoretical calculations, which yield magnetic moment of 7.0 μ B/f.u. for Gd 3+ ion and 0.18 μ B/f.u. for conduction electrons with magnetic moment of the same direction as the Gd moment. An anomalous spontaneous magnetostriction is dominating the thermal expansion behavior below T C. In particular, we have observed a large contraction in the c-direction and a smaller expansion in the a and b directions (nearly identical). The unit cell volume expands below T C (Δ V/ V=8×10 −4). The observed anisotropy of the magnetostriction in GdNi is attributed to anisotropic magnetoelastic coupling.