Exchange stiffness constant and effective gyromagnetic factor of Gd, Tb and Nd containing, amorphous rare earth-transition metal films

The exchange stiffness constant and the effective gyromagnetic factor of amorphous Gd/sub 13.5/Tb/sub 6.2/Fe/sub 80.3/, Gd/sub 21.2/Co/sub 78.8/, Gd/sub 19.4/Nd/sub 6.1/Fe/sub 74.5/ and Gd/sub 19.6/Nd/sub 10.3/Fe/sub 70.1/ alloy films have been determined by Brillouin light scattering and from measurements of the domain wall energy. All samples, which show a constant Curie temperature of 465 K, exhibit the same exchange stiffness constant, as measured by Brillouin light. The obtained values of both methods agree Gd/sub 13.5/Tb/sub 6.2/Fe/sub 80.3/ and Gd/sub 21.2/Co/sub 78.8/ films, but not for the Nd containing films. The latter is attributed to a breakdown of the standard Bloch domain wall equation in Nd containing systems.>