Random fields in the diluted Ising system Fe_1-xMg_xCl₂

We discuss how random fields (RFs) are generated in uniaxial random antiferromagnets by applied fields and report a systematic specific heat study on the three-dimensional (3-D) system Fe1-xMgxCl2 to demonstrate their effects. The RF crossover exponent ø is determined by measuring the shape of the phase boundary in the TH plane and we obtain ø=1.26 ± 0.10, in agreement with theoretical prediction. Drastic changes in the shape of the specific anomaly are observed. We argue that they are due to the temperature dependence of the random fields. © 1983.