Tunnel Magnetoresistance Effect in Tunnel Junctions with Co2MnSi Heusler Alloy Electrode and MgO Barrier
We demonstrated that a large TMR ratio of 753 % has been observed at 2 K in a MTJ using a Co2MnSi Heusler alloy electrode and a crystalline MgO tunnel barrier. At room temperature (RT), we also have observed a large TMR ratio of 217 %, which value at RT is much larger than that of MTJs using an amorphous Al-oxide tunnel barrier. However, the temperature dependence of the TMR ratio was still large. In order to improve the interface, we investigated the TMR effect in Co2MnSi/CoFeB(0–2 nm)/MgO/CoFe MTJs. TMR ratio was enhanced by inserting a thin CoFeB layer at the Co2MnSi/MgO interface. The MTJ with CoFeB thickness of 0.5 nm exhibited the highest TMR ratio. From the conductance–voltage measurements for the fabricated MTJs, we inferred that the highly spin polarized electron created in Co2MnSi can conserve the polarization through the 0.5 nm thick FeB layer.
KeywordsHeusler Alloy Magnetic Tunnel Junction Tunneling Magnetoresistance Transmission Electron Micrograph Image Coherent Tunneling
We would like to thank all our collaborators in the DFG research unit FG 559. This work would be the result of efforts of all members. This study was supported by DFG FG 559 (project P12) and the Strategic Japanese–German Cooperative Program on Nanoelectronics by JST as the matching fund. Also, the part of this work was supported by the High-Performance Low-Power Consumption Spin Devices and Storage Systems program under Research and Development for Next-Generation Information Technology, and Grand-in-Aid for Scientific Research for Priority Area Creation and Control of Spin Current by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT). This research was partly conducted at the Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University.
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