Spin resonance and magnetic susceptibility of amorphous Gd _xY_0.33-xAl_0.67 films showing spin-glass behavior

Abstract

The effects of dilution of Gd by Y in a series of evaporated amorphous GdxY0.33-xAl0.67 films (x from 0.33 to 0.0027) has been studied by microwave magnetic resonance and SQUID magnetometry. The SQUID measurements show a spin glass freezing temperature Tf of 13.5K for x = 0.33 and 6.5K for x = 0.16, with Tf being less than 1.6K or nonexistent for samples with x<0.04. X-band microwave measurements reveal a line broadening ΔH and an increasing g-shift as the temperature T is lowered. These low temperature effects are interpreted in terms of a theory by Salamon which permits determination of the spin-spin relaxation time τ∝xm/(T-Tf)n. Contrary to earlier experimental or theoretical indications, we find m∼-0.5 and n∼1.5.