Bias dependence of spin transfer torque in Co2MnSi Heusler alloy based magnetic tunnel junctions

Abstract

Heusler compounds are of interest as electrode materials for use in magnetic tunnel junctions (MTJs) due to their half metallic character, which leads to 100% spin polarization and high tunneling magnetoresistance. Most work to date has focused on the improvements to tunneling magnetoresistance that can stem from the use of Heusler electrodes, while there is much less work investigating the influence of Heusler electrodes on the spin transfer torque properties of MTJs. Here, we investigate the bias dependence of the anti-damping like and field-like spin transfer torque components in both symmetric (Co2MnSi/MgO/Co2MnSi) and asymmetric (Co2MnSi/MgO/CoFe) structure Heusler based MTJs using spin transfer torque ferromagnetic resonance. We find that while the damping like torque is linear with respect to bias for both MTJ structures, the asymmetric MTJ structure has an additional linear component to the ordinarily quadratic field like torque bias dependence and that these results can be accounted for by a free electron tunneling model. Furthermore, our results suggest that the low damping and low saturation magnetization properties of Heusler alloys are more likely to lead significant improvements to spin torque switching efficiency rather than their half metallic character.

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“…Typical hard FM saturated magnetization and crystalline anisotropy values were chosen. The spin injection efficiency of the FM layers was chosen to be consistent with Heusler alloys [31]- [33]. A high Gilbert damping was chosen consistent with the value used in [8].…”

Convolutional Neural Networks Utilizing Multifunctional Spin-Hall MTJ Neurons

“…The various physical parameters for the simulation are found in Table I. Magnetic values consistent with Heusler alloys were chosen [15]- [17]. The power consumption in a MAAP set is dominated by the I 2 R loss caused by the input currents passing through their respective weight resistors.…”

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“…All nonfundamental parameters used in the simulation are given in Table I. The saturation, anisotropy and spin injection efficiency of the FM layers were chosen to be consistent with Heusler alloys [30]- [32]. The conversion length chosen is between the value reported for Ag/Bi interfaces [12] and those of novel 2D materials such as MoS2 monolayers [22].…”