Abstract
Current-induced magnetization reversal via spin-orbit torques (SOTs) has been intensively studied in heavy-metal/ferromagnetic-metal/oxide heterostructures due to its promising application in low-energy consumption logic and memory devices. Here, we systematically study the function of Joule heating and SOTs in the current-induced magnetization reversal using Pt/Co/SmOx and Pt/Co/AlOx structures with different perpendicular magnetic anisotropies (PMAs). The SOT-induced effective fields, anisotropy field, switching field and switching current density (Jc) are characterized using electric transport measurements based on the anomalous Hall effect and polar magneto-optical Kerr effect (MOKE). The results show that the current-generated Joule heating plays an assisted role in the reversal process by reducing switching field and enhancing SOT efficiency. The out-of-plane component of the damping-like-SOT effective field is responsible for the magnetization reversal. The obtained Jc for Pt/Co/SmOx and Pt/Co/AlOx structures with similar spin Hall angles and different PMAs remains roughly constant, revealing that the coherent switching model cannot fully explain the current-induced magnetization reversal. In contrast, by observing the domain wall nucleation and expansion using MOKE and comparing the damping-like-SOT effective field and switching field, we conclude that the current-induced magnetization reversal is dominated by the depinning model and Jc also immensely relies on the depinning field.
Highlights
Manipulating magnetization reversal in a perpendicularly magnetized heavy metal (HM)/ferromagnetic metal (FM) structure by current-induced spin-orbit torques (SOTs) has attracted considerable attention in recent years due to its potential application in high density and low energy dissipation storages compared with the conventional spin-transfer-torque (STT) devices[1,2,3,4,5,6]
In order to gain more insight on the function of the Joule heating and SOT in the current-induced magnetization reversal process, we quantitatively explore the relationships between Hsw, SOT, and Jc, which will be described in the part
We have investigated the roles of the Joule heating and current-induced spin-orbit torque played in the current-induced magnetization reversal in Pt/Co/SmOx and Pt/Co/AlOx structures with different perpendicular magnetic anisotropies
Summary
Manipulating magnetization reversal in a perpendicularly magnetized heavy metal (HM)/ferromagnetic metal (FM) structure by current-induced spin-orbit torques (SOTs) has attracted considerable attention in recent years due to its potential application in high density and low energy dissipation storages compared with the conventional spin-transfer-torque (STT) devices[1,2,3,4,5,6]. Some reports reveal that θSH could be tuned by varying the thickness of HM15,30, decorating the interface between HM and FM16,31,32, changing the crystallinity of HM33 and even involving oxygen in HM34 Most of these studies can be boiled down to strengthen the driving force for the magnetization reversal and thereby improve the switching efficiency with a lower switching current density. The influences of Joule heating on the depinning field and current-induced magnetization reversal in SOT-based devices were rarely reported and usually ignored[41,42]. The current-induced Joule heating, which behaves like the temperature, plays an assisted role in the magnetization reversal by decreasing depinning field and increasing SOT efficiency
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