VALENCE-BAND AND SB 4D CORE-LEVEL PHOTOEMISSION OF THE XMNSB-TYPE HEUSLER COMPOUNDS (X=PT, PD, NI)

Electronic structures of the valence band and Sb 4d core levels of the XMnSb-type Heusler alloys (where X = Pt, Pd, Ni) have been investigat ed systematically using photoemission spectroscopy (PES) and self-cons istent spin-polarized band structure calculations. The extracted Mn 3d PSW of XMnSb (where X = Pt, Pd) are found to be almost identical. Int erestingly, they are quite different from those of Mn metal, but are a nalogous to those of MnO, suggesting that the role of the Sb 5p electr ons in XMnSb may be similar to that of the O 2p electrons in MnO. A co mparison of the PSW with the corresponding theoretical angular momentu m projected density of states (PLDOS) shows a fairly good agreement fo r the Pt and Pd d states, but large discrepancies for the Mn and Ni 3d states. The calculated X d and Mn 3d PLDOS reveal that the hybridizat ion between the Mn 3d and X d states increases from X = Pt to Pd and N i. In the Sb 4d core level PES spectra, a broader and less structurele ss line shape is observed for X = Pd than for X = Pt and Ni. A detaile d analysis of their line shapes indicates that it is due to a larger l ifetime broadening for X = Pd than for X = Pt and Ni.