## Abstract

We first present a scaling argument for the relaxation times in spin glasses, as suggested by Binder and Young. We emphasize the relevance of our dynamic measurements near the magnetic field-temperature transition line to equilibrium properties such as the nonlinear susceptibility. We show how, in the insulating system Eu_{0.4}Sr_{0.6}S, the phase lag of the ac susceptibility with respect to the modulated field relates the measuring frequency ω to a characteristic response time τ. We are thus able to define the zero field freezing temperature, T_{f}(ω). Two scaling models are tested, appropriate to a finite critical temperature, T_{c}, and to a zero temperature transition. Respectively, this leads to two critical slowing down regimes: τ/τ_{0} ∼ (T - T_{c})^{-zv} and ln(τ/τ_{0}) ∼ T^{ -zv}. Both are shown to be consistent with the data, and to lead to T_{c} = 1.50 K, zv = 8, τ_{0} = 3x10^{-12} s; or T_{c} = 0, zv = 9 and τ _{0} = 10^{-8} s. The set of parameters derived for the former (finite T_{c}) case appears to be more consistent with previous data on Eu_{0.4}Sr_{0.6}S, and with recent computer simulations. We then generate, in the magnetic field-temperature plane, lines T_{f} (ω, H) associated with the response time τ. We include remanent magnetization measurements which refer to well defined experimental time scales (≤1 s or ≤25 s). The entire set of scaled data, for the case when T_{c} = 1.50 K, strongly suggests that the response time diverges for H^{ 1 2} ∼ T - T_{c}. This is of the form of a de Almeida-Thouless transition line with, however, a non-mean-field exponent.

Original language | English (US) |
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Pages (from-to) | 1-5 |

Number of pages | 5 |

Journal | Journal of Magnetism and Magnetic Materials |

Volume | 54-57 |

Issue number | PART 1 |

DOIs | |

State | Published - Feb 1986 |

Externally published | Yes |

## ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics