Spin-polarized tunneling in a half-metallic ferromagnet

Direct measurement of the conduction electron spin polarization (P) in epit axial NiMnSb was performed to test the prediction of half metallicity in th is material. Spin-polarized tunneling in NiMnSb/Al2O3/Al junctions showed P of 28%, contrary to the predicted value of 100%. Magnetoresistance measure ments in NiMnSb/Al2O3/Ni80Fe20 junctions concurred with this result. The di screpancy between theory and experiment is discussed. Also, the latter junc tions show four nonvolatile remanent states due to the NiMnSb magnetocrysta lline anisotropy, which has potential as four-level logic elements. (C) 199 9 American Institute of Physics. [S0021-8979(99)02623-7].