Local and bulk magnetic properties of amorphous ferromagnetic Gd2Co obtained by splat cooling

We present the results of N.M.R., bulk magnetization and susceptibility measurements on amorphous Gd2Co obtained by splat-cooling. This alloy is ferromagnetic below a Curie temperature Tcof 172 (±3) °K as measured by an inductance bridge. Tcis determined more accurately from detailed magnetization measurements in the vicinity of the transition by using a thermodynamic parameters method. Values thus obtained for the critical exponents β, γ and δ were found to be close to the values calculated in a 3d-Heisenberg model. The saturation magnetization at 4.2°K is 212 (±2) emu/g, which yields a moment μGd=7.07 (±0.07)μB/Gd at., if one assumes that μCois zero. The effective moment deduced from the Curie-Weiss law at high temperature is 8.4μBper Gd at. (assuming μCo=0). The paramagnetic Curie temperature is 183°K. Spin-echo N.M.R. measurements were performed at 1.3°K in zero field. A broad line (half-width 35 MHz) centered at 70 MHz is attributed to the resonance of Co⁵⁹nuclei. Thus, the hf field at Co⁵⁹nuclei is slightly larger in amorphous Gd2Co than in crystalline GdCo2, where μCois known to be 1.02 (±0.03)μB. Such a high value for hf field in the amorphous case might originate from conduction electron polarization by neighbouring Gd atoms.