Magnetism in transition metals at finite temperatures. I. Computational model

Abstract

Considerable evidence indicates that in Fe above the Curie temperature the electron system forms local magnetic moments which are relatively stable in magnitude and rotate to destroy long-range order. The local moments arise from exchange polarisation of the electron gas in a similar way to the conventional picture of the ferromagnetic ground state of the metal. The authors set up a one-electron-like Hartree-Fock-like model with a Stoner-like intra-atomic exchange interaction for calculating the electronic structure of such a system with arbitrary directions for the atomic moments. The directions for a cluster of 500-1000 atoms are assumed and fed into the calculation, from which the magnitudes of the moments are computed self-consistently using Haydock's recursion method (1980). The total energies are also obtainable. Results are presented for two simple types of magnetic configuration: spin spirals represent a smooth variation of the direction of magnetisation whereas alternating tilts form a rough variation back and forth from atom to atom.