  Dynamic magnetic properties and ageing phenomena of the re-entrant
ferromagnet (Fe0.20Ni0.80)75P16B6Al3 are investigated by time dependent zero
field cooled magnetic relaxation, m (t), measurements. The influence of a
temperature cycling (perturbation), +/- *T, (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.
