POLARIZATION ANALYSIS OF THE MAGNETIC EXCITATIONS IN INVAR AND NON-INVAR AMORPHOUS-ALLOYS

Conventional spin wave theory works remarkably well in describing the spin dynamics of both Invar and non-Invar isotropic ferromagnets, with the important exception that for Invar systems the magnetization decr eases much more rapidly with temperature than can be explained based o n the measured spin wave dispersion relations. We have been carrying o ut triple-axis polarized inelastic neutron scattering experiments on t he amorphous ferromagnets Fe86B14 (Invar system) and Fe40Ni40P14B6 (ME TGLAS(R) 2826) in order to separate the longitudinal magnetic fluctuat ions from the transverse (spin wave) excitations, and thereby determin e if the presence of longitudinal excitations might resolve this discr epancy. The present measurements exhibit longitudinal excitations belo w T(c), but in both materials. Possible interpretations of the results are discussed.