Critical order-parameter relaxation in EuS, a nearly isotropic ferromagnet

Abstract

From high-frequency (1.6-1900 MHz) dispersion measurements between the critical isochore (H=0, T>or=Tc) and the critical isotherm (H>or=0, T=Tc) of EuS, the sample-shape-independent kinetic coefficient of the homogeneous magnetization, Gamma , is derived. Presenting Gamma (H,T) in terms of the static susceptibility chi ( omega =0; H,T), all data collapse onto a single curve. At large chi the kinetic coefficient approaches conventional behaviour, whereas near chi =1 a gradual decrease is observed, which appears to be indicative of the critical speeding-up predicted for Gamma (H=0,T) of isotropic ferromagnets.