Scaling of susceptibility and the size of the critical region in an amorphous GdAl spin glass (invited)

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Abstract
We extend our earlier SQUID magnetometry studies of the susceptibility of amorphous Gd37A63 spin glass to a temperature range 5≤T≤100 K and a field range 0.5≤H<50 000 Oe. This enables us to determine the size of the critical region around the spin glass transition at TG=15.5 K; it extends to approximately 22 K in temperature and 15 000 Oe in field. We show that the range of reduced temperature t=(T−TG)/TG for spin glass critical behavior is determined by the parameter 1/Z1/2, where Z is the number of interacting neighbors, in rough agreement with experiment, and that the field range can be estimated from a crossover relation Hαtφ/2. We also find that nonanalyticity in χ(H) as H→0 persists at all temperatures below TG and argue that this can cause apparent nonanalyticity above TG as well in the presence of sample inhomogeneity.

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