Remanent Magnetization of an Insulating Spin Glass: Eu0.4Sr0.6s
We report on the time (10-6 < t < 103 s), temperature (1.3 < T < 2K) and magnetic field (1 < H < 1 000 0e) dependence of the thermoremanent magnetization (TRM) of the insulating spin-glass Eu0.4Sr0.6S (Tf = 1.55 K) deduced from Faraday rotation measurements. The TRM is fitted over several decades of time with a power law MR = At-a which, however, fails near from Tf and it varies linearly with T for low fields (H < 8 0e). We have demonstrated that the unusual field dependence of the TRM always found in spin-glass systems, i.e. MR (H) has a maximum, is only due to the increase with H of the demagnetization rate which compensates, at high fields, the larger initial magnetization. Our data agree qualitatively with recent Monte Carlo simulation studies and cannot be analysed on the basis of independent two level systems. This suggests a cooperative behavior below Tf.
KeywordsAnisotropy Remanent Magnetization AuFe
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