Angular Magnetic-Field-Dependent Tunneling Magnetoresistance Controlled by Electric Fields in an MTJ/PMN-PT Multiferroic Heterostructure

作者：Wang, Shaoting; Yang, Yuanjun^*; He, Lanping; Li, Wanyu; Jiang, Yang; Wang, Chi; Li, Lu; Wei, Chong; Sun, Yuchen; Ge, Weifeng; Jia, Cheng; Zhang, Hui; Wang, Lan^*

来源：Journal of Electronic Materials, 2023, 52(4): 2645-2654.

DOI：10.1007/s11664-023-10226-y

• Multiferroic heterostructure
• magnetic tunnel junction
• angular tunneling magnetoresistance
• electric-field control
• magnetization switching
• magnetoelectric coupling

The electric-field modulation of magnetization switching is an energy-efficient method for the design of potential spintronic devices. In this study, a magnetic tunnel junction (MTJ)/Pb(Mg1/3Nb2/3)(0.7)Ti0.3O3 (PMN-PT) magnetoelectric heterostructure with the memory configuration of the MTJ was constructed for electric-field control of magnetization switching through angular-dependent magnetotransport measurements. It was observed that the electric-field control of tunneling magnetoresistance (TMR) depends on the direction of the applied magnetic field, and the corresponding tunability (T) of the TMR ratio will also change as the angle between the applied magnetic field and the x-axis changes. When a maximal electric field of 8.6 kV/cm is applied to the PMN-PT layer with a magnetic field (similar to 50 Oe) along the major axis direction of the MTJ (i.e., PMN-PT [100]), the tunability T-major (the subscript refers to the major axis) is approximately +0.17 parts per thousand. However, when a magnetic field (similar to 50 Oe) is applied along the minor axis direction of the MTJ (i.e., PMN-PT [01-1]), the tunability T-minor is approximately -1.8 parts per thousand. Furthermore, the tunability T-minor (the subscript refers to the minor axis) first increases with a positive sign and then decreases with a negative sign as the applied magnetic fields increase. It further increases negligibly as the magnitude of the applied magnetic field increases. The corresponding transitional region is in the range of approximately 15-40 Oe. It is conjectured that the competition among electric-field-induced magnetoelastic anisotropy, magnetic shape anisotropy, and Zeeman energy induced by the external magnetic field contributes to the magnetization switching of the free layer in the MTJ. This results in the aforementioned electric-field control of the TMR behavior. The findings from this study can help in understanding the mechanism of electric-field-induced magnetic switching in storage-mode MTJs through strain-mediated magnetoelectric coupling.