CrO2-based heterostructure and magnetic tunnel junction: perfect spin filtering effect, spin diode effect and high tunnel magnetoresistance

Half-metallic ferromagnetic CrO2 has attracted much interest due to its 100% spin polarization and high Curie temperature. CrO2 films have been fabricated on a TiO2 (100) substrate. However, there have been no reports on the spin transport properties of devices based on a CrO2 electrode and TiO2 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 CrO2/TiO2 (100) heterostructure and the CrO2/TiO2/CrO2 (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 x 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.