MAGNETIC EXCITATIONS AT THE SURFACE OF ALLOYS WITH 2 FERROMAGNETIC COMPONENTS

Low-temperature magnetic excitations at the surface of an alloy of two ferromagnets are studied. A model Heisenberg Hamiltonian with nearest-neighbor interactions only is considered. The cluster-Bethe-lattice method of solution is applied to the specific case of the (110) surface of a body-centered-cubic alloy. The effects of surface segregation are given particular attention. One of the results is that, for cases in which the surface segregated element is that of larger magnetic moment, it is possible to find a range of temperatures for which the surface is magnetically harder than the bulk. The case of the FeCo alloy is examined along these lines and it is found that, since Fe tends to segregate at the surface, the surface should have a larger magnetization for temperatures up to ∼400 K. © 1979 The American Physical Society.