Field‐Free Switching of Magnetization by Tilting the Perpendicular Magnetic Anisotropy of Gd/Co Multilayers

Abstract

Efficient current‐induced switching of perpendicular magnetization is an essential task in spintronics for realizing high‐performance information processing and for storage device application. However, the spin‐orbit torque (SOT) by injection of in‐plane polarized spins cannot deterministically switch the magnetization of ferromagnetic thin films with perpendicular magnetic anisotropy (PMA) without an additionally applied in‐plane external magnetic field to break the symmetry of the PMA. Considering the difficulties of applying the magnetic field to the localized area only within a device structure, it is essential to contrive a facile field‐free SOT switching mechanism. Here, deterministic field‐free SOT switching of perpendicular magnetization is achieved in amorphous and ferrimagnetic Gd/Co multilayers accompanied by a tilted magnetic anisotropy axis. This tilted anisotropy originates from the combined contributions of many internal anisotropies in different orientations from the multilayers and is shown to be controllable. It is expected that the introduction of controlled tilted anisotropy into Gd/Co multilayers over the entire film surface in the present study can be extended to the development of wafer‐scale technologies for the spintronics memory and logic devices.

Growth-Dependent Interlayer Chiral Exchange and Field-Free Switching

“…This reciprocal effect manifests itself as a shift in the IMA hysteresis loop, similar to PMA layer's behavior (See Supplemental Material S1). From the applied in-plane field |H φ | dependence of Hoffset, we also rule out the possibility of a tilted easy axis effect scenario that could also give rise to a similar yet linear M IMA -independent Hoffset [34,35] (See Supplemental Material S2).…”

“…The symmetry of a PMA magnetization is normally preserved under current-induced SOT if the spin polarization direction is constrained in-plane without the usage of unconventional spin polarizations [37], therefore field-free switching cannot be realized. Prior to our work, numerous methods were proposed to break the mirror symmetry and to achieve a purelycurrent-driven magnetization switching, such as utilizing an intralayer DMI [38], tilted magnetic anisotropy [35,39], exchange bias [40][41][42][43] and epitaxial materials with broken mirror symmetry [37,44]. It is postulated here that when the IMA layer experiences magnetization switching, the interlayer DMI effective field will reverse its polarity as well, potentially assist in breaking the symmetry between up/down magnetization states or switching the PMA magnetization outright.…”

Hydrogen-Controlled Spin Reorientation Transition in a Nanometer-Thick FePd Layer on Co/[Pt/Co]4/Pt Multilayers for Applications in Spintronics

“…10 Recently, Hwang et al demonstrated the deterministic field-free SOT switching of perpendicular magnetization in amorphous and ferrimagnetic Gd/Co multilayers accompanied by a tilted magnetic anisotropy (TMA) axis, disrupting the symmetry of the PMA in a controlled manner, and providing an opportunity for switching perpendicular magnetization by using tilted anisotropy. 11 In this experiment, we demonstrated the field-free reorientation of TMA films at room temperature in FePd/ Co/[Pt/Co] 4 /Pt multilayer structures grown on a SiO 2 substrate by the introduction of a hydrogenation effect. 12 Due to the high affinity of Pd to hydrogen gas, the magnetic properties of Pd-based magnetic alloys can be reversed by hydrogen, providing a strategy for controlling the PMA.…”

“…Numerous efforts have been made to realize field-free SOT switching mechanisms, including achieving lateral structural asymmetry using a wedge-layer, − voltage control in a multiferroic composite, exchange-bias and interlayer exchange coupling, and current-induced field-free switching . Recently, Hwang et al demonstrated the deterministic field-free SOT switching of perpendicular magnetization in amorphous and ferrimagnetic Gd/Co multilayers accompanied by a tilted magnetic anisotropy (TMA) axis, disrupting the symmetry of the PMA in a controlled manner, and providing an opportunity for switching perpendicular magnetization by using tilted anisotropy …”

Enhanced Spin–Orbit Torque Performances in PtRu–Co–PtRu–Ni–Ru-Based Spintronic Devices

“…The research studies on spin–orbit torque (SOT) have drawn great attention in the field of spintronic industries since its discovery. , Based on the spin-Hall effect or Rashba effect, it provides another approach to switch magnetic moments in the adjacent ferromagnetic layer. − Usually, the SOT-based devices consume less energy and have better stabilities. Thus, the research studies on SOT are typically concentrated on the magnetic storage devices. − In the SOT-based spintronic devices, the alloyed heavy metal (HM) layers are commonly used as the source of spin current. − In our previous work, the Pt 80 Ru 20 -alloyed HM layer was confirmed with a lower energy consumption and an optimized SOT performance .…”