Magnetic ordering in amorphous Nd-Co, Gd-Co and Er-Co alloys

Abstract

Previous studies of magnetism in amorphous rare earth–transition metal alloys have emphasized alloys rich in transition metal. We report here results on three rare earth rich amorphous alloys: Nd64Co36, Gd65Co35, and Er65Co35. Low field susceptibility, χ, was measured for T in the range 4.2 K⩽T⩽300 K and magnetization was measured for 1.3⩽T⩽200 K and applied fields, H, of 0⩽H⩽80 kOe. Curie-Weiss fits were made to high temperature χ (T) data to determine average effective moments and Weiss temperatures. Hysteresis loops were used to determine the coercive force and the ordering temperatures, TC. The effective moments and saturation moments are compared with values calculated on the assumption of local moments on both the rare earth and Co ions. TC values for Nd, Gd, and Er alloys are 38 K, 170 K, and 12 K, respectively. The data are consistent with a ferrimagnetic structure in Gd65Co35. Local random anisotropy appears to play an important role in the Nd-Co and the Er-Co alloys.