Spin-dependent resonant tunneling of multiferroic tunnel junction via head-to-head 180° domain wall

Abstract

The extraordinary properties of the two-dimensional electron gas (2DEG) at oxide heterostructure interface such as LaAlO3/SrTiO3 have attracted considerable investigations. Recent work suggested that the 2DEG could be formed within the SrTiO3 tunnel barrier by replacing the central TiO2 atomic layer with LaO, and that such a tunnel junction exhibits resonant tunneling behavior with new intriguing properties and potential applications [J. D. Burton et al., Phys. Rev. B 80, 115408 (2009)]. Here we investigate an alternative approach providing the resonant transmission of which a 180° head-to-head (HH) domain wall in the middle of the tunnel barrier induces the 2DEG via the free electronic carriers screening the polarization bound charges in situ. Using first-principles calculations on the Fe/PbTiO3/Fe as a model system, we show that this strategy allows for the formation of a 2DEG within the barrier, and that the remarkable difference between the majority- and minority-spin channels results in large tunneling magnetoresistance (TMR) effect. The resonant tunneling and the large TMR effect are beneficial to magnetic recording applications. We also discuss the feasibility to obtain such a 180° HH domain wall in the practical magnetic tunnel junctions and the influences of FeO formation at the iron-complex oxide interface on the electronic structure and tunneling properties.