Magnetism in Amorphous Terbium‐Iron

Neutron diffraction and magnetization measurements on a sputtered specimen of 33% terbium, 66% iron have confirmed the existence of long range magnetic order and an amorphous spatial distribution of atoms and spin sites. Elastic diffraction data taken above and below the 409K Curie temperature have enabled the separation of nuclear and magnetic scattering contributions. The magnetic spin density function contains a very broad major peak, dominated by the Tb‐Tb pair distribution function, with a maximum near 3.6 A. Longer range correlations are very much weaker. The principal features of the atomic structure can be accounted for by considering only near neighbor correlations between terbium and iron atoms in a random close‐packed arrangement. Inelastic scattering studies have revealed a significant shift in the magnetic density of states to lower energy in the amorphous material relative to the crystal‐ line TbFe2 counterpart. No discrete spin‐wave excitations or critical scattering near Tc could be observed.