TUNNELING EVIDENCE OF HALF-METALLIC FERROMAGNETISM IN LA0.7CA0.3MNO3

Direct experimental evidence of half-metallic density of states (DOS) is observed by scanning tunneling spectroscopy on ferromagnetic La0.7C a0.3MnO3, which exhibits colossal magnetoresistance (CMR). Tunneling c onductance data taken at 77 K, well below the Curie temperature T-C ap proximate to 260 K, show close resemblance to the spin-split DOS spect rum calculated for the itinerant bands in the ferromagnetic state. The half-metallic spectral characteristics are absent in the paramagnetic state at room temperature, as well as in the undoped antiferromagetic compound LaMnO3, which shows no CMR. These results directly implicate the half-metallic ferromagnetism in the phenomenon of CMR.