Entropy Changes of Ferromagnetic-Antiferromagnetic Transitions from Magnetic Measurements

Abstract

The thermodynamics of magnetic processes in several compounds undergoing ferro‐ or ferrimagnetic to antiferromagnetic transitions are studied using critical field‐transition temperature data obtained with a miniature‐coil, pulsed‐field technique. The zero‐field transition entropy change in each material is calculated by means of the magnetic Clapeyron equation. The results are discussed in terms of the Kittel theory of exchange inversion. The variation of exchange constant α with lattice parameter c is found to vary over only a small range, and is roughly proportional to the reciprocal of the sublattice magnetization.