Coexistance of giant tunneling electroresistance and magnetoresistance in an all-oxide magnetic tunnel junction

TL;DR

This paper demonstrates that large tunneling magnetoresistance and electroresistance effects can coexist in an all-oxide magnetic tunnel junction, with the SrTiO3 layer controlling both effects, enabling potential four-state memory devices.

Contribution

The study shows that TMR and TER effects can simultaneously occur in an all-oxide device, with SrTiO3 layer thickness controlling both phenomena, which is a novel approach for memory applications.

Findings

TMR originates from spin filtering by BaTiO3 barrier.

TER is enabled by intercalating SrTiO3 at the interface.

SrTiO3 thickness scales with both TMR and TER effects.

Abstract

We demonstrate with first-principles electron transport calculations that large tunneling magnetoresistance (TMR) and tunneling electroresistance (TER) effects can coexist in an all-oxide device. The TMR originates from the symmetry-driven spin filtering provided by the insulating BaTiO3 barrier to the electrons injected from SrRuO3. In contrast the TER is possible only when a thin SrTiO3 layer is intercalated at one of the SrRuO3/BaTiO3 interfaces. As the complex band-structure of SrTiO3 has the same symmetry than that of BaTiO3, the inclusion of such an intercalated layer does not negatively alter the TMR and in fact increases it. Crucially, the magnitude of the TER also scales with the thickness of the SrTiO3 layer. The SrTiO3 thickness becomes then a single control parameter for both the TMR and the TER effect. This protocol offers a practical way to the fabrication of four-state memory cells.