Electronic structure calculations for a rare earth-transition metal amorphous alloy system

In order to clarify the origin of the Kerr effect for a rare earth-transition metal (RE-TM) amorphous alloy system, electronic structure calculations were performed for the first time in an amorphous system including f orbitals. Tb20Fe80 and Nd20Fe80 amorphous alloy compositions were chosen for the present work. The electronic structures were calculated by using the most localized linear muffin-tin orbital method based on atomic sphere approximation and the recursion method. To evaluate the first excited f states of rare-earth metals, it was assumed that the occupied f electrons were sufficiently localized in the inner core of a RE atom to be treated as core electrons. The calculated density of states for a Tb20Fe80 amorphous alloy shows good agreement with reported experimental results measured by x-ray photoelectron spectroscopy (XPS) and inverse XPS. In particular, the unoccupied f-state level and the hybridization property between the Tb d state and the Fe d state were well reproduced. The calculated electronic structure for Nd20Fe 80 reveals that the enhancement of the Kerr effect at a light wavelength of around 300 nm in a Nd alloy system originates from the interband transition from d to f state.