THEORETICAL DESCRIPTION OF THE MAGNETOCALORIC EFFECT IN Mn-Fe-P-Si ALLOYS

摘要

We apply a thermodynamic model describing magnetoelastic effects and based on mean field theory tornunderstand the physical origin of the first order ferro- to paramagnetic magnetostructural transition occurringrnin Mn1.3Fe0.65P0.5Si0.5. The phenomenological parameters of the model are determined through comparisonrnwith the entropy data measured by Peltier calorimetry under magnetic field. The values obtained support thernidea that: the phase transition is driven by the strong magnetoelastic coupling present along the a lattice axis;rnthe spin entropy plays a key role in the transition; the structural contribution has a minor counteracting role.rnMoreover, the number of magnetic moments derived from the model agrees with the picture describing thernparamagnetic phase of the system as due to the disordered magnetic moments at the Mn sites only.