Atomistic theory of the critical field for intrinsic spin reversal in transition metals

A method to estimate the critical field for intrinsic spin reversal in transition metals is proposed within the framework of itinerant-electron magnetism. By studying the transverse magnetic susceptibility under a Hartree-Fock approximation, the dispersion relations of the spin wave excitations are obtained, which possess a positive gap induced by the anisotropically coupled spin-orbit interaction when the magnetization is along the easy axis. When a magnetic field applied opposite to the magnetization is strong enough to overcome the excitation gap, a spin reversal transition takes place which defines the critical field. To illustrate the present method, transition-metal magnetic monolayers and microclusters have been examined. Comparisons show that the method can be applied to capture effects missed in the classical Stoner treatment.