Photoemission study of electron correlation in M7X8 (M=Fe, Co; X=S, Se)

The occupied and unoccupied states of ferrimagnetic metals Fe7S8 and Fe7Se8 , and a paramagnetic metal Co7Se8 have been studied by photoemission and X- ray inverse photoemission spectroscopies. Compared with the density of stat es (DOS) given by the band-structure calculation, the photoemission spectra of Fe 3d and Co 3d are narrowed. While the Fe 3d photoemission spectrum ha s a strong intensity at the higher binding energy side, it is significantly suppressed near the Fermi level. Self-energy corrections to the DOS's have been done for Fe7Se8 and Co7Se8. Disagreements between experimental and th eoretical spectra have become small, indicating the importance of electron correlation effect. (C) 1999 Elsevier Science B.V. All rights reserved.