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

Abstract

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 × 10¹⁴%) 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.