Static critical exponents of the ferromagnetic transition in spin glass re-entrant systems

TL;DR

This study investigates the static critical exponents near the Curie temperature in re-entrant ferromagnetic alloys, revealing deviations from classical models and suggesting a weak universality class for these systems.

Contribution

It provides experimental measurements of critical exponents in re-entrant ferromagnetic alloys, highlighting deviations from the 3D Heisenberg model and proposing a weak universality class.

Findings

Exponents differ significantly from 3D Heisenberg predictions

Values are intermediate between ferromagnetic and spin glass transitions

A weak universality class may describe these re-entrant systems

Abstract

The static critical phenomenology near the Curie temperature of the re-entrant metallic alloys Au_0.81Fe_0.19, Ni_0.78Mn_0.22, Ni_0.79Mn_0.21 and amorphous a-Fe_0.98Zr_0.08 is studied using a variety of experimental techniques and methods of analysis. We have generally found that the values for the exponents alpha, beta, gamma and delta depart significantly from the predictions for the 3D Heisenberg model and are intermediate between these expectations and the values characterizing a typical spin glass transition. Comparing the exponents obtained in our work with indices for other re-entrant systems reported in the literature, a weak universality class may be defined where the exponents distribute within a certain range around average values.