HIGH D-BAND OCCUPANCY IN ALLOYS OF MG WITH SOME 4D-TRANSITION AND 5D-TRANSITION METALS - A PHOTOEMISSION-STUDY

Photoemission data from co-sputtered films of binary alloys of Ru, Rh, Pd, Ir, Pt and Au with Mg show that the transition metal (TM) d band narrows as the TM concentration is reduced, reaching a minimum after which the intensity decreases but the width remains constant. The continuity of binding energy, spin-orbit splitting and width of the resulting d states suggests a high level of d-band occupancy in all cases. LMTO bandstructure calculations for pure Tm and ordered intermetallic compounds of the form MgTM and Mg3TM also show narrowing of the d bands, with binding energies and widths which indicate that they are fully, or nearly fully occupied in all cases where the TM is dilute. We suggest that the additional d intensity results from a spread of the TM d wavefunctions on to the surrounding Mg sites, allowing high d-band occupancy whilst preserving charge neutrality.