Abstract
The temperature-pressure phase diagram of iron is analysed in terms of the microscopic contributions to the free energy, i.e. vibrational, electronic and magnetic excitations. It is shown that the thermodynamic data, when combined with other experimental and theoretical information, require persistent disordered localized magnetic moments in the paramagnetic bcc, fcc and liquid phases but not so for the hcp phase. The bcc-fcc transitions are mainly caused by differences in the electronic and magnetic free energies while the vibrational part plays a minor role.