Thermodynamic transformations in magnetically polarizable undeformable media

In this paper the problem of magnetically undeformable polarizable media in the presence of an electromagnetic field is analyzed from a thermodynamic viewpoint. The thermodynamic transformations are explicited as functions in the state space in which one of the variables, characterizing the magnetic polarization, is given as an internal variable. The entropy form along the thermodynamic transformation is calculated for para- and diamagnetic media and the necessary conditions for its existence are given.