A molecular dynamics approach to magnetic alloys with turbulent complex magnetic structures: alloys

Abstract

A molecular dynamics (MD) approach to magnetic alloys with complex magnetic structures is proposed on the basis of the temperature control MD method and the functional integral technique. The theory allows us to determine automatically the magnetic structure of a large system with a few hundred atoms in a unit cell. Numerical calculations for alloys have been performed using 108 atoms in a unit cell. It is demonstrated that alloys form various complex magnetic structures due to competing interactions: the `first-kind' antiferromagnetic structure for less than 20 at.% Fe, the helix-like structure for 20 at.% Fe, noncollinear structures between 30 and 60 at.% Fe, the collinear-like structure for 65 at.% Fe, noncollinear structures between 70 and 80 at.% Fe, collinear structures between 85 and 95 at.% Fe, and the helical structure for . The average magnetic moments calculated from these structures are shown to explain the concentration dependence - in particular, the existence of the peculiar minimum of the average magnetic moment at 50 at.% Fe.