Molecular-dynamics approach to itinerant magnetism with complex magnetic structures

A molecular-dynamics (MD) theory of itinerant magnetism which describes the complex magnetic systems with a large number of atoms in a unit cell is proposed on the basis of the isothermal molecular-dynamics method and the functional integral method. The MD approach allows us to predict automatically the complex magnetic structure with a few hundred atoms in a unit cell at finite temperatures. It is demonstrated by the numerical calculations for bcc Fe that the MD approach describes the second-order phase transition as a function of temperature because of a self-consistent effective medium in the theory. The application of the theory to the fcc transition metals with the use of 108 atoms and 256 atoms shows the existence of various complex magnetic structures for the d-electron numbers between 6.0 and 7.0 and the existence of strong spin frustrations in γ-Fe because of the competing magnetic interactions.