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VOLUME 65 | ISSUE 5 | PAGE 430
The possibility of a very large magnetoresistance in half-metallic oxide systems
The tunnel magnetoresistance (TMR) is analyzed for ferromagnet-insulator-ferromagnet junctions, including novel half-metallic systems with 100% spin polarization. Direct tunneling is compared with impurity-assisted and resonant TMR. Direct tunneling in iron group systems leads to about a 20% change in resistance, as observed experimentally. Impurity-assisted tunneling decreases the TMR down to 4% with Fe-based electrodes. A resonant tunnel diode structure would give a TMR of about 8%. The model applies qualitatively to half-metallics, where the change in resistance in the absence of spin-flips may be arbitrarily large and even in the case of imperfect magnetic configurations the resistance change can be several thousand percent. The examples of half-metallic ferromagnetic systems are / and Cr02/Ru02, and a discussion of their properties is presented. PACS: 73.40.Gk, 73.61.-r, 75.70.Pa