DIRECT EVIDENCE FOR A HALF-METALLIC FERROMAGNET

Half-metallic materials are characterized by the coexistence of metall ic behaviour for one electron spin and insulating behaviour for the ot her. Thus, the electronic density of states is completely spin polariz ed at the Fermi level, and the conductivity is dominated by these meta llic single-spin charge carriers. This exotic physical property could have a significant effect on technological applications related to mag netism and spin electronics. Some ferromagnetic systems, such as Heusl er compounds(1) and chromium dioxide(2), have been predicted theoretic ally to be half-metallic. However, a half-metallic system has not been demonstrated directly and the predictions are still in doubt(3,4). He re we report spin-resolved photoemission measurements of a ferromagnet ic manganese perovskite, La0.7Sr0.3MnO3, which directly manifest the h alf-metallic nature well below the Curie temperature. For the majority spin, the photoemission spectrum clearly shows a metallic Fermi cut-o ff, whereas for the minority spin, it shows an insulating gap with dis appearance of spectral weight at similar to 0.6 eV binding energy.