Change of concavity of the field temperature transition lines at short times in the Eu0.4Sr0.6S spin glass

Abstract

We report on the transverse and longitudinal response in Eu0.4Sr 0.6S with a small a.c. field (102-105 Hz) superimposed to a large static one. From the onset of the imaginary susceptibility, we derive transition lines, identical in both configurations, which exhibit, at low field, a reversed curvature more pronounced with increasing frequency. The isotropy of the response is assigned to the dipolar interaction. Our results are compared to mean field theory and numerical simulations