Magnetoresistance in MgO-based magnetic tunnel junctions with Fe, Co, and FeCo – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2008 > Magnetoresistance in M...

Magnetoresistance in MgO-based magnetic tunnel junctions with Fe, Co, and FeCo

We use spin-density functional theory and non-equilibrium Green's functions to estimate the structure and low-bias current/voltage characteristics of magnetic tunnel junctions (MTJs) consisting of five-layer MgO barriers sandwiched between Fe, Co and FeCo electrodes in both the parallel and anti-parallel magnetization configurations. The calculated tunneling magnetoresistance (TMR) decreases with increasing bias voltage in all three MTJs in the bias range considered (0 - 0.5 V). In the FeCo/MgO system it remains constant below V _ 0.3 V. While the calculated value of the TMR is roughly a factor of 10 larger than found in experiments, the decrease in TMR with bias is in agreement with experimental observations. The tunneling mechanisms behind this bias dependence are discussed in terms of the electronic structure of the electrodes.

Ph.D. defence by Morten Stilling