Voltage Control of Perpendicular Exchange Bias in Multiferroic Heterostructures

TL;DR

This paper demonstrates voltage-controlled perpendicular exchange bias in multiferroic heterostructures at room temperature, revealing strain-mediated effects and ionic gating as effective modulation methods for high-density spintronic applications.

Contribution

It introduces a room-temperature fabrication process for voltage-tunable perpendicular exchange bias and explores strain and ionic liquid gating effects on the interfacial magnetic coupling.

Findings

Voltage-induced lattice distortion transmits to the AFM/FM interface.

Charge accumulation via gating produces a large hysteresis offset.

Perpendicular EB can be effectively modulated at room temperature.

Abstract

Perpendicular exchange bias (EB), which combines the perpendicular magnetic anisotropy and the ferromagnetic (FM) - antiferromagnetic (AFM) exchange coupling, is extremely important in the high-density AFM spintronics. However, the effective modulation of EB remains challenging, since the alternant spins at the AFM/FM interface are strongly pinned by the AFM layer. Voltage tuning of EB through the magnetoelectric coupling provides a potential way to achieve a rapid magnetization switching in an energy-efficient manner. Nevertheless, the interfacial strain mediation of perpendicular EB induced by E-field remains unexplored. In this work, we obtain perpendicular EB nanostructure by room-temperature fabrication process, and demonstrate the voltage tunable perpendicular EB in Pt/IrMn/(Co/Pt)2/Ta/(011) Pb(Mg1/3Nb2/3)O3-PbTiO3 multiferroic heterostructure. To enhance the voltage control effect on perpendicular EB, we further investigate both strain-mediated magnetoelectric coupling and ionic liquid gating method in the thinned EB system with the structure of Pt/IrMn/Co/Pt/Ta. As a result, the voltage induced lattice distortion effectively transmits to the AFM/FM interface, while the charge accumulation in gating method generates a relatively large hysteresis loop offset that has not been observed before at room temperature. The voltage manipulation of perpendicular EB at room temperature provides new possibilities towards novel AFM devices and memories with great energy-efficiency and ultra-high density.