OBSERVABILITY OF A QUASI-LINEAR TEMPERATURE-DEPENDENCE OF THE MAGNETIZATION IN A SEMI-INFINITE FERROMAGNET

Current theory [Rado, Phys. Rev. B. 40, 407 (1989)] shows that the existence of magnetic surface anisotropy leads to surface spin waves which can provide a mechanism for quasilinear temperature dependence of the magnetization (M(T)) near the surface of a semi-infinite ferromagnet. Since volume spin waves as well as surface spin waves are excited thermally, we now generalize this theory in two ways. First, we include in the calculation the effects of both surface and volume spin waves; and second, we include the effects of both of the surface anisotropy constants K(ss) and K(s). The fractional magnetization deviation (M(o)-M(T))/M(o) caused by the volume spin waves competes, of course, with that caused by the surface spin waves. We find that for all allowed values of K(s) and K(ss) it is mostly at very low temperatures that the contribution to (M(o)-M(T))/M(o) arising from surface spin waves is comparable to the contribution to (M(o)-M(T))/M(o)arising from volume spin waves. This result depends on the assumption that the material parameters are independent of position throughout the sample volume.