Anomalous behavior of electron-spin resonance on a spin glass at Tg

Abstract

We report measurements on Ag Mn spin glass (10.3 at% Mn) for 0.1 T g < T < 1.6 T g at multiple frequencies between 0.6 and 9.5 GHz. For T < T g, the isotherms in a diagram of frequency ω/2π vs. resonant field intersect the ω-axis at ω ≠ 0, like in antiferromagnets. This indicates the existence of an anisotropy energy (density) or constant K. The isotherms above T g, however, meet the origin, denoting that K(H = 0) = 0. An anisotropy constant K( H ≠ 0) ≠ 0 above T g is attributed to the critical fluctuations suppressed by the static applied field. The anomalous behavior of the linewidth at T g is also discussed qualitatively.