Time correlation function for a Cu-Mn spin glass

Abstract

The self-correlation function xi (t) for a Cu-3 at.% Mn alloy has been determined with good statistical accuracy using conventional time-of-flight as well as the more sophisticated backscattering technique. Around the low-frequency (10 Hz) freezing temperature T_f the correlation function xi (t) shows a power-law decay, i.e. xi (t)=at^-v with nu approximately 0.25 above T_f, but nu =0.1+or-0.02 and just below T_f. At lower temperatures (T/T_f approximately=0.75) xi (t) is best expressed as xi (t)=at^-v+b log(t) and yields nu =0.4+or-0.1. At still lower temperatures (Tf) xi (t) can be expressed as xi (t)=c+at^-v, with a value of nu which is consistent with nu approximately 0.5, predicted by recent mean-field theories as well as computer simulations. An important result of the measurements is that the mean correlation time tau ₁e/ obeys the Vogel-Fulcher law suggesting a glass-like transition with T_g approximately=0.8 T_f(10 Hz).