Experimental energy-band dispersions and magnetic exchange splitting for cobalt

Abstract

We have determined E vs k energy-band dispersions of cobalt for s and d bands along the hexagonal axis A ([0001] direction) via angle-resolved photoelectron spectroscopy from a Co(0001) face using synchrotron radiation. We obtain the magnetic exchange splitting at for the upper d band (0.85 0.2 eV) and lower d band (1.2 0.3 eV). The overall occupied d-band width (3.8 eV at L) is about 20% narrower than a state-of-the-art self-consistent band calculation using a local-density theory of exchange correlation. The top of the majority-spin d bands is 0.35 eV below EF. There is a small centered minority-electron pocket at EF which explains previously unidentified de Haas-van Alphen orbits. We present dipole selection rules for the axis of an hcp lattice and show that the number of allowed transitions is reduced drastically for emission along the axis. The allowed transitions can be interpreted in the same way as those for emission normal to a (111) face of an fcc lattice. © 1980 The American Physical Society.