Tunnel Magnetoresistance Over 100% in MgO-Based Magnetic Tunnel Junction Films With Perpendicular Magnetic L1$_{0}$-FePt Electrodes

Perpendicular L1<sub>0</sub>-FePt/MgO/Fe/L1<sub>0</sub> -FePt magnetic tunnel junction (MTJ) films with the (001) texture were successfully developed to obtain a large tunnel magnetoresistance (TMR) above 100 % at room temperature. The TMR ratio in the L1<sub>0</sub>-FePt/MgO/Fe/L1<sub>0</sub>-FePt MTJ was strongly dependent on the Fe interfacial layer thickness. The lattice mismatch between the MgO(001) barrier layer and the L1<sub>0</sub> -FePt(001) layer is too large for the MgO barrier layer to grow epitaxially on the L1<sub>0</sub>-FePt(001) layer. The insertion of the Fe interfacial layer improves the quality of the MgO(001) barrier layer and achieves an epitaxy in the L1<sub>0</sub>-FePt/MgO/Fe/L1<sub>0</sub>-FePt stack. As a result, the optimization of the Fe interfacial layer thickness is a key to obtain the large TMR ratio in the MgO-based MTJ with the L1<sub>0</sub>-FePt electrodes.

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