Magnetism of an Fe monolayer on W(110)

We discuss theoretical studies of magnetism in the Fe monolayer adsorbed on the W(110) surface. We first present density-functional studies of the ground state that provide us with basic magnetic parameters, under the assumption the ground state is ferromagnetic. We provide results for the spin and orbital magnetic moments, local density of states, the anisotropy, and measures of the exchange strength as provided by calculations of the energy difference between the ferromagnetic and antiferromagnetic states. We compare these results with those provided by the empirical tight-binding description we have used to describe spin waves in this system, to find good agreement between the two methods where results overlap. Inclusion of spin-orbit coupling within our tight-binding Hamiltonian produces anisotropy close in strength and character to that which emerges from the full density-functional analysis, for example. We then present new calculations of the nature of the spin waves in the monolayer. We point out that the large anisotropy that emerges from our analyses (similar to that found in earlier work), combined with our calculations of the effective exchange, provides a value for the Curie temperature of the film much larger than that found experimentally. An earlier experimental study has suggested that in this system, the effective exchange is much smaller than we find. We conclude that the magnetism in this much studied system is not well understood. We discuss reasons why this may be so.