Appearance potential study of PrMn2 and SmMn2 intermetallics

Abstract

Soft X-ray appearance potential spectroscopy (SXAPS) has been employed to study the changes in the electronic structure of PrMn2 and SmMn2 intermetallics as a result of aloying. In this technique the total X-ray emission associated with the thresholds for the excitations of core levels of the atoms in the surface region of the materials is measured. It sensitively provides information regarding the density of unoccupied states at the Fermi level. The SXAPS spectra of the M4,5 levels of Pr and Sm and the L2,3 levels of Mn in these intermetallics are compared with the corresponding elemental spectra. The observed shift in the core levels represents contribution from the shifts due to charge transfer and that due to the hybridization between the Mn 3d and the rare earth 5d bands. The charge transfer shifts have been estimated from the differences in the Fermi levels of the intermetallic and the element using the free electron model. These values have been utilized to obtain the hybridization shifts. The hybridization shifts show a decreasing trend in these intermetallics and is attributed to the decrease in the number of electrons in the 3d–5d hybridized bands. Our results correlating the Mn magnetic moment with the number of electrons are consistent with the reported experimental data. It is concluded that the 3d–5d hybridization plays a significant role in determining the magnetic properties of these intermetallics.