Precise interface engineering using a post-oxidized ultrathin MgAl layer for
the voltage-controlled magnetic anisotropy effect
Takayuki Nozaki,
Tomohiro Nozaki,
Hiroshige Onoda,
Hiroyasu Nakayama,
Tomohiro Ichinose,
Tatsuya Yamamoto,
Makoto Konoto,
Shinji Yuasa
Affiliations
Takayuki Nozaki
Research Center for Emerging Computing Technologies, National Institute of
Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568,
Japan
Tomohiro Nozaki
Research Center for Emerging Computing Technologies, National Institute of
Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568,
Japan
Hiroshige Onoda
Research Center for Emerging Computing Technologies, National Institute of
Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568,
Japan
Hiroyasu Nakayama
Research Center for Emerging Computing Technologies, National Institute of
Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568,
Japan
Tomohiro Ichinose
Research Center for Emerging Computing Technologies, National Institute of
Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568,
Japan
Tatsuya Yamamoto
Research Center for Emerging Computing Technologies, National Institute of
Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568,
Japan
Makoto Konoto
Research Center for Emerging Computing Technologies, National Institute of
Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568,
Japan
Shinji Yuasa
Research Center for Emerging Computing Technologies, National Institute of
Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568,
Japan
The voltage-controlled magnetic anisotropy (VCMA) effect has been proposed as an energy efficient approach for controlling the direction of magnetization. To demonstrate the scalability of a voltage-controlled magnetoresistive random access memory, we need to optimize the perpendicular magnetic anisotropy (PMA), tunnel magnetoresistance (TMR), and VCMA properties. Here, we performed a systematic investigation of the effects of inserting a post-oxidized MgAl layer on PMA, TMR, and VCMA in epitaxial magnetic tunnel junctions (MTJs). PMA and TMR have substantial dependences on the thickness of the MgAl layer, and their maximum values occurred when the MgAl layer was 0.20 nm thick, resulting in threefold and twofold increases in the PMA energy and TMR ratio, respectively, compared with the case without a MgAl layer. On the other hand, the VCMA coefficient increased as the MgAl layer thickness decreased and had a maximum value of −350 fJ/Vm when the MgAl layer was 0.16 nm thick, suggesting that the weakly oxidized interface provides a larger VCMA effect. Interface engineering using a post-oxidized ultrathin MgAl layer provides us with a valuable technique for precisely controlling the PMA, TMR, and VCMA properties of voltage-controlled MTJs.
