APPEARANCE-POTENTIAL STUDY OF PRMN2 AND SMMN2 INTERMETALLICS

Soft X-ray appearance potential spectroscopy (SXAPS) has been employed to study the changes in the electronic structure of PrMn2 and SmMn2 i ntermetallics as a result of alloying. In this technique the total X-r ay emission associated with the thresholds for the excitations of core levels of the atoms in the surface region of the materials is measure d. It sensitively provides information regarding the density of unoccu pied states at the Fermi level. The SXAPS spectra of the M(4,5) levels of Pr and Sm and the L(2,3) 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 char ge transfer and that due to the hybridization between the Mn 3d and th e 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 d ecreasing trend in these intermetallics and is attributed to the decre ase in the number of electrons in the 3d-5d hybridized bands. Our resu lts correlating the Mn magnetic moment with the number of electrons ar e consistent with the reported experimental data. It is concluded that the 3d-5d hybridization plays a significant role in determining the m agnetic properties of these intermetallics.