Field dependence of the magnetocaloric effect in materials with a second order phase transition: A master curve for the magnetic entropy change

Abstract

The field dependence of the magnetic entropy change can be expressed as SM Hn. For soft magnetic amorphous alloys n=1 well below the Curie temperature TC , n=2 in the paramagnetic range, and n 0.75 for T=TC. The first value can be explained with simple arguments, n=2 is a consequence of the Curie-Weiss law, but n TC deviates from mean field predictions. From the Arrott-Noakes equation of state, a relation between n TC and the critical exponents has been obtained, showing remarkable agreement with experimental data for an example alloy, predicted n=0.72 versus experimental n=0.73 . A master curve behavior for the temperature dependence of SM measured for different maximum fields is proposed.