Thermodynamics

Abstract

It is clear from the preceding chapters that the relative population of the lowest energy levels of paramagnetic ions depends on both the temperature and the strength of the external magnetic field. The equilibrium states of a system can often be described by three variables, of which only two are independent. For the common example of the ideal gas, the variables are pVT (pressure, volume, temperature). For magnetic systems, one obtains HMT (magnetic field, magnetization, temperature) as the relevant variables and the thermodynamic relations derived for a gas can be translated to a magnetic system by replacing p by H and V by — M. In the next section we review a number of the thermodynamic relations. Then, two sections are used to demonstrate the usefulness of these relations in analyzing experiments. In fact the simple thermodynamic relations are often applicable, even to magnetic systems that require a complicated model to describe the details of their behavior [1].