Boron Composition Dependence of Spin-Transfer Switching in Magnetic Tunnel Junctions with CoFeB Free Layers

概要

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We investigated tunnel magnetoresistance (TMR) and magnetization switching due to spin-transfer torque in CoFeB/MgO/CoFeB junctions having three different free layer compositions, (Co50Fe50)100-xBx ($x = 20$, 25, 30), and measured their magnetic properties, including magnetization ($M_{\text{s}}$) and Gilbert damping constant ($\alpha$), which are theoretically predicted to contribute to the critical current density ($J_{\text{c0}}$) for spin-transfer switching. We found that the $J_{\text{c0}}$ in the magnetic tunnel junctions (MTJs) with $x = 30$ became smaller than that in the MTJs with $x = 20$ despite having a lower TMR ratio and a larger $\alpha$. We showed that the $J_{\text{c0}}$ for each composition tends to follow the theoretical relationship for the magnetic factor of the free layer.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2009-01-25