Deviations from Perfect Memory in Spin Glass Temperature Cycling Experiments

We study the deviations from perfect memory in negative temperature cycle spin glass experiments. It is known that the a.c. susceptibility after the temperature is raised back to its initial value is superimposed to the reference isothermal curve for large enough temperature jumps ∆T (perfect memory). For smaller ∆T , the deviation from this perfect memory has a striking non monotonous behavior: the ‘memory anomaly’ is negative for small ∆T ’s, becomes positive for intermediate ∆T ’s, before vanishing for still larger ∆T ’s. We show that this interesting behavior can be reproduced by simple Random Energy trap models. We discuss an alternative interpretation in terms of droplets and temperature chaos. PACS. 75.50.Lk Spin glasses and other random magnets – 05.70.Fh Phase transitions: general studies – 64.70.Pf Glass transitions