Abstract
We present a theoretical investigation of the magnetisation reversal process in CoFeB-based magnetic tunnel junctions (MTJs). We perform atomistic spin simulations of magnetisation dynamics induced by combination of spin orbit torque (SOT) and spin transfer torque (STT). Within the model the effect of SOT is introduced as a Slonczewski formalism, whereas the effect of STT is included via a spin accumulation model. We investigate a system of CoFeB/MgO/CoFeB coupled with a heavy metal layer where the charge current is injected into the plane of the heavy metal meanwhile the other charge current flows perpendicular into the MTJ structure. Our results reveal that SOT can assist the precessional switching induced by spin polarised current within a certain range of injected current densities yielding an efficient and fast reversal on the sub-nanosecond timescale. The combination of STT and SOT gives a promising pathway to improve high performance CoFeB-based devices with high speed and low power consumption.
Highlights
We present a theoretical investigation of the magnetisation reversal process in CoFeB-based magnetic tunnel junctions (MTJs)
In this work we investigate the influence of the combined spin transfer torque (STT) and spin orbit torque (SOT) phenomena on the magnetisation switching dynamics of CoFeB/MgO-based MTJs at the atomistic level, whose details can be found in the “Methods” section
By means of this approach we have modelled and investigated the magnetisation dynamics resulting from the combined action of spin orbit torque and spin transfer torque in CoFeB/MgO MTJs
Summary
We present a theoretical investigation of the magnetisation reversal process in CoFeB-based magnetic tunnel junctions (MTJs). To overcome the limitation of an external magnetic field in SOT-MRAMs, field-free switching has been proposed by controlling the geometry of the d evice[26], introducing a tilted magnetic a nisotropy[27], using in-plane MTJs28 and T-type s tructures[29], exploiting the exchange bias via coupling of the ferromagnetic layer with an antiferromagnet[30], combining VCMA with SHE-induced SOT in in-plane M TJs31, using a magnetic hard mask to shape the SOT track[32]. Downsides of these solutions are the scaling of the cell size and the limited efficiency[26,30] and in some cases difficulties of integration in the current CMOS technology. The design requires MTJ in-plane dimensions to be reduced and the writing still requires the application of an-plane magnetic field
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