CrO 2 -based heterostructure and magnetic tunnel junction: perfect spin filtering effect, spin diode effect and high tunnel magnetoresistance.

Half-metallic ferromagnetic CrO 2 has attracted much interest due to its 100% spin polarization and high Curie temperature. CrO 2 films have been fabricated on a TiO 2 (100) substrate. However, there have been no reports on the spin transport properties of devices based on a CrO 2 electrode and TiO 2 barrier. In this work, we use first-principles calculations combined with a nonequilibrium Green's function method to investigate the bias-voltage-dependent spin transport properties for the CrO 2 /TiO 2 (100) heterostructure and the CrO 2 /TiO 2 /CrO 2 (100) magnetic tunnel junction (MTJ). Our results reveal the excellent spin filtering effect and spin diode effect in the heterostructure as well as the high tunnel magnetoresistance ratio (up to 4.48 × 10 14 %) in the MTJ, which indicate potential spintronic applications. The origins of these perfect spin transport characteristics are discussed in terms of the calculated spin-dependent electrode band structures, the spin-dependent transmission spectra and semiconductor theory.