On the latent heat of high-temperature spin reorientation transitions

If a 3d-4f magnet experiences a spin reorientation at a high temperature, it proceeds in an abrupt fashion, as a first-order phase transition, and is accompanied by release or absorption of heat. It is demonstrated that this latent heat amounts to two times the anisotropy constant of the 3d sublattice. This prediction is corroborated by the available experimental data. The same approach provides an estimate for the accompanying entropy change, which suggests that spin reorientation transitions cannot compete in this respect with ferromagnetism-paramagnetism or ferro-magnetism-antiferromagnetism transitions. (c) 2007 American Institute of Physics.