Sensitivity to temperature perturbations of the ageing states in a re-entrant ferromagnet

Dynamic magnetic properties and ageing phenomena of the re-entrant ferromagnet (Fe0.20Ni0.80)75P16B6,Al3 are investigated by time dependent zero field cooled magnetic relaxation, m(t). measurerments. The influence of a. temperature cycling (perturbation); ±deltaT, (prior the field application) on the relaxation rate is investigated both in the low temperature re-entrant spin glass "phase" and in the ferromagnetic phase. In the ferromagnetic phase the influence of a positive and a negative temperature cycle (of equal magnitude) on the response is almost the same (symmetric response). The result at lower temperatures, in the RSG "phase" is asymmetric, with a strongly affected response for positive; and hardly no influence on the response for negative temperature cycles. The behaviour at low temperatures is similar to what is observed in ordinary spin glasses.