Magnetocaloric effect at the exchange–inversion with magnetoelastic coupling

We develop a thermodynamic model to describe antiferro- (AFM) to ferromagnetic (FM) phase transitions through magnetoelastic coupling in the framework of Kittel's exchange–inversion mechanism. By including both magnetic and structural contributions to the free energy, we derive the conditions to have a direct AFM–FM transition. These are represented either by the presence of a non-zero intra-sublattice coupling constant or by a sufficiently high value of the magnetoelastic coupling parameter. In the paper we establish these conditions by analytical means and we discuss the physical meaning of the model in relation to possible applications to magnetocaloric materials with AFM–FM transitions