Measurement of complex susceptibility on a metallic spin glass with broad relaxation spectrum

Abstract

AC susceptibility measurements (0.625 H z⩽ v ⩽625 H z) have been performed in a SQUID magnetometer on the amorphous metallic spin glass (Fe 0.06Ni 0.94) 75P 16B 6Al 3. The in-phase component of the susceptibility ( x') shows a sharp peak at the spin glass freezing temperature T g≈8 K with a frequency dependence of ▵ T g/ T g≈0.015 per decade of frequency increase. The out-of-phase component ( x″) exhibits a small anomaly at the spin glass transition with the magnitude of the anomaly almost independent of frequency. In particular we find the relation x″=( π;/2)ϑ x'/ϑ lnω to be valid in the vicinity of T g. This relation and a frequency independence of x″ are fundamental characteristics of a spin glass having a broad spectrum of relaxation times. We argue that similar results from ac susceptibility measurements should be found in many spin glass systems, metallic as well as non-metallic.