Landau theory of magnetic phase diagrams and first order magnetisation processes

The Landau free energy expansion up to sixth order in the magnetisation has been used to study ferro- and paramagnetic phases in zero and finite applied magnetic fields. Magnetic phase diagrams are determined in terms of Landau coefficient ratios which indicate first order and metamagnetic phase transitions. In addition the critical magnetic field and specific magnetisations corresponding to first order magnetisation processes are calculated in terms of these coefficients. A method of evaluating Landau coefficients is also demonstrated.