Direct Observation of the Exchange-Split Virtual Bound State in Dilute Mn Alloys

The majority- and minority-spin states of the exchange-split virtual bound state of Mn impurities in Cu and Ag are studied with high-resolution photoemission and bremsstrahlung isochromat spectroscopy. The exchange splitting is found to be close to the atomic value. The majority-spin state is strongly hybridized with the host-metal $d$ band resulting in its delocalization. The minority-spin states are localized but close to the Fermi level so that a description of the physical properties in terms of a spin Hamiltonian is not appropriate.