Theory of metallic magnetism at finite temperatures in bulk materials and thin films

Abstract

A review of ‘first-principles’ theoretical work that describes the properties of magnetic metallic materials at finite temperatures is given. The key assumption is that a time-scale separation can be identified. There are the thermally induced spin fluctuations which are long-lived compared to the time electrons take to move from one lattice site to another. The dependence on the spin-polarised electronic structures of the systems is emphasised including the role of ‘local exchange splitting’ inferred even in the paramagnetic states. The disordered local moment picture which provides the basis of a mean field theory is discussed and its results for bulk transition metals and alloys recalled. Finally, new results for this picture in metallic thin films are reported. In particular comparison with calculated magnetic ordering temperatures of iron films on copper substrates is made with those deduced from experiment and an interpretation in terms of the electronic structure is given.