2018年度 提案書 （Web公開用）

作成者： 温振超（東北大CSRN）

研究プロジェクト名： Voltage control of magnetic anisotropy in spintronic
heterostructures (スピントロニクヘテロ構造における磁気異方性の電圧制御に関する研究)
概 要 ： Voltage or electric field control of magnetic anisotropy in spintronic
heterostructures is a promising technology for achieving energy-efficient spintronicdevices. In this research, we will study the electric effect in magnetic heterostructuresfabricated by engineering materials and interfaces for the purpose of enhancing
performance of spintronic devices.
コアメンバー： 温振超（東北大）、三谷グループ（NIMS）、高梨グループ（東北大）
期待される研究成果：

Spintronicdevices with the structure of normal metal(NM)/ferromagnet (FM)/Barrier/FM will
be investigated, as shown in the illustration.
When a voltage is applied, the magnetic
anisotropy of the FM layer will be changed.
By engineering materials and interfaces inthe structure, the electronic band
structures and spin-orbit interactions canbe manipulated. In a well-designed
heterostructure, a large voltage or electricfield effect on the magnetic anisotropy of
FM layers could be expected.

2017年度 報告書 （Web公開用）

作成者： 温 振超 （東北大CSRN）

研究プロジェクト名：
Voltage control of magnetic anisotropy in magnetic
heterostructures (磁気ヘテロ構造における磁気異方性の電圧制御に関する研究)
概要： Voltage control of magnetic anisotropy (VCMA) in magnetic heterostructures is one of key

technologies for achieving energy‐efficiency electronic devices. Here, we report the first demonstration of
the VCMA effect in epitaxial Ru/Co2FeAl (CFA)/MgO heterostructures. A VCMA coefficient of 108 fJ/Vm for
the CFA film was achieved at room temperature (RT). Also, the VCMA was studied in an ultrathin Fe(001)monocrystalline layer sandwiched between Cr and MgO. A large coefficient of the electric field effect ofmore than 200 fJ/Vm was observed for the Fe layer at RT.

研 究 成 果 （ 実 施 状 況 ） ： Perpendicularly
magnetized tunnel junctions with the structure of
Ru/CFA/MgO were fabricated, as illustrated in Fig. (a).
An effective voltage control on switching fields for
the CFA layer was observed in Fig. (b). The interfacialstability was confirmed and the temperaturedependence of the VCMA was investigated.
Furthermore, the VCMA was studied in the structureof Cr/Fe/MgO as shown in Fig. (c). A large coefficientof VCMA of more than 200 fJ/Vm was achieved in Fig.
(d). Interestingly, nonlinear behavior was found in theelectric field dependence, being independent of post‐annealing and measurement temperatures. The
studies contribute to the progress in applications andtheoretical studies on VCMA‐based spintronic devices.

主要発表論文等： [1] Z. Wen et al., Sci. Rep. 7, 45026 (2017).
[2] Q. Xiang, Z. Wen et al., J. Phys. D: Appl. Phys. 50, 40LT04 (2017).

2018年度 報告書 （Web公開用）

作成者： 温 振超（物質・材料研究機構）

Voltage control of magnetic anisotropy in spintronic
研究プロジェクト名：heterostructures (スピントロニクヘテロ構造における磁気異方性の電圧制御に関する研究)
概要： Voltage control of magnetic anisotropy (VCMA) is a promising technology for achieving
energy-efficient spintronic devices. In this work, we studied the VCMA effect in Cr/Fe/MgAlOx
magnetic heterostructures fabricated by molecular beam epitaxy (MBE). Distinct VCMA effects
were observed as a function of Fe thickness, which could be attributed to electronic structures in
the heterostructure. This work may contribute to develop further large VCMA effect for
spintronic devices.
研究成果（実施状況）： Voltage control ofmagnetic anisotropy (VCMA) in spintronic
heterostructures with the structure of
Cr/Fe/MgAlOx/Fe was investigated, as shownin the illustration. A large VCMA effect withthe maximum coefficient of -390 fJ/Vm wasachieved at tFe = 0.7 nm. It is also found thatthe sign of VCMA effect strongly depends on
the thickness of bottom Fe layer, as shown in
the figures. The mechanism could be thedifference in electronic structures in theheterostructure. Detailed analysis andunderstanding could be important for thedevelopment of further large VCMA effect.

主要発表論文等： [1] Z. Wen et al., Adv. Electron. Mater. 3, 1700367 (2018).
[2] Z. Wen et al., arXiv:1902.07406