Electronic Structures of Fe3-xVxSi Probed by Photoemission Spectroscopy

Heusler-type ternary and pseudobinary compounds Y2ZX ( Y and Z denote transition metal atoms and X is a metalloid) in the L21 or DO3 structure, which exhibit remarkable “site-selectivity” properties, have received renewed interest owing to their ferromagnetic shape memory, half-metallic electronic structure and thermoelectric properties etc. Among them, Fe3-xVxSi (0 ≤ x ≤ 1) alloys show some remarkable electronic and magnetic property. It is known that magnetic structure of Fe3-xVxSi changes from ferromagnetic to antiferromagnetic ones with increasing the content of nonferromagnetic V. It is also reported that Fe3-xVxSi compounds show anomalous resistivity properties 1) and negative Seebeck coefficient (thermoelectric power) at larger x 2). In order to clarify the origin of these novel properties of Fe3-xVxSi alloys in terms of the electronic structures, the valence-band as well as core-level photoelectron spectroscopy has been performed at BL-23SU of SPring-8 with soft X-ray and at BL-29XU of SPring-8 with hard X-ray. In this study it is to be clarified that the main structures of 1s, 2p core level spectra of Si, Fe and V shift to the higher binding energy with the addition of the V concentration due to the chemical potential shift; as for the spectra of valence band, with the increase of V concentration, the main structures shift to higher binding energy, which should be the evidences for the movement of Fermi level to higher energy; the high resolution X-ray photoemission spectra also show that the intensity around Fermi level decreases with adding V, and a new sharp structure formed for x = 1, which indicate the formation of pseudo-gap at large x. The comparisons of experimental valence band spectra with those of the total DOS calculated with KKR-CPA method 1) are also done in this study. *This work was done under the approval of the SPring-8 Proposal Assessing Committee (Proposal No. 2005B3811）and was also supported by the Ministry of Education, Culture, Sports, Sciences and Technology of Japan. 1) Y. Nishino, et al, Phys. Rev. B 48, (1993)13607. 2) O. Nashima, et al, J. Alloys Compd., 383, (2004)298. 3) A. Bansil, et al, Phys. Rev. B 60, (1999)13396.