631% room temperature tunnel magnetoresistance with large oscillation effect in CoFe/MgO/CoFe(001) junctions

We demonstrate tunnel magnetoresistance (TMR) ratios of up to 631% at room temperature (RT) using CoFe/MgO/CoFe(001) epitaxial magnetic tunnel junctions (MTJs). The TMR ratio increased up to 1143% at 10 K. The large TMR ratios resulted from fine-tuning of atomic-scale structures of the MTJs, such as crystallographic orientations and MgO interface oxidation by interface insertion of ultrathin CoFe and Mg layers, which are expected to enhance the well-known & UDelta;(1) coherent tunneling transport. Interestingly, the TMR oscillation effect, which is not covered by the standard coherent tunneling theory, also became significant. A 0.32-nm period TMR oscillation with increasing MgO thickness dominates the transport in a wide range of MgO thicknesses; the peak-to-valley difference of the TMR oscillation exceeds 140% at RT, which is attributed to the appearance of large oscillatory components in the resistance area product.

Automated summary

We demonstrate high tunnel magnetoresistance (TMR) ratios of up to 631% at room temperature (RT) and 1143% at 10 K using CoFe/MgO/CoFe(001) epitaxial magnetic tunnel junctions (MTJs). The large TMR ratios are achieved through fine-tuning of atomic-scale structures and through the insertion of ultrathin CoFe and Mg layers, which enhance coherent tunneling transport and contribute to the significant TMR oscillation effect. The oscillation phenomenon dominates the transport behavior and can reach a peak-to-valley difference exceeding 140% at RT.