MOLECULAR-DYNAMICS APPROACH TO ITINERANT MAGNETISM WITH COMPLEX MAGNETIC-STRUCTURES

A molecular-dynamics (MD) theory of itinerant magnetism which describe s the complex magnetic systems with a large number of atoms in a unit cell is proposed on the basis of the isothermal molecular-dynamics met hod and the functional integral method. The MD approach allows us to p redict automatically the complex magnetic structure with a few hundred atoms in a unit cell at finite temperatures. It is demonstrated by th e 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 fee transition metals with the use of 108 atoms and 256 atoms shows the existence of various complex magnetic structures f or the d-electron numbers between 6.0 and 7.0 and the existence of str ong spin frustrations in gamma-Fe because of the competing magnetic in teractions.