Micromagnetic simulation of exchange coupled ferri-/ferromagnetic heterostructures

While current-induced spin-orbit torques (SOTs) have been extensively studied in ferromagnets and antiferromagnets, ferrimagnets have been less studied. Here we report the presence of enhanced spin-orbit torques resulting from negative exchange interaction in ferrimagnets. The effective field and switching efficiency increase substantially as CoGd approaches its compensation point, giving rise to 9 times larger spin-orbit torques compared to that of noncompensated one. The macrospin modelling results also support efficient spin-orbit torques in a ferrimagnet. Our results suggest that ferrimagnets near compensation can be a new route for spinorbit torque applications due to their high thermal stability and easy current-induced switching assisted by negative exchange interaction. * eleyang@nus.edu.sg

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“…To validate the above model, macrospin simulations were performed by solving two coupled Landau-Lifshitz-Gilbert (LLG) equations [54,55]. Fig.…”

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confidence: 99%

Anomalous Current-Induced Spin Torques in Ferrimagnets near Compensation

et al. 2017

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“…15 To understand the continuous change in J sw , we consider a simple model where the magnetization dynamics in the alloy is described by two strongly antiferromagnetically coupled sublattices a and b, subjected to the SOT. The magnetization dynamics is described by modified LLG equations 20 including the damping-like SOT and a coupling term as…”

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confidence: 99%

Spin-orbit torque-induced switching in ferrimagnetic alloys: Experiments and modeling

Rojas-Sánchez

Pham

et al. 2018

Applied Physics Letters

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We investigate spin-orbit torque (SOT)-induced switching in rare-earth-transition metal ferrimagnetic alloys using W/CoTb bilayers. The switching current is found to vary continuously with the alloy concentration, and no reduction in the switching current is observed at the magnetic compensation point despite a very large SOT efficiency. A model based on coupled Landau-Lifschitz-Gilbert (LLG) equations shows that the switching current density scales with the effective perpendicular anisotropy which does not exhibit strong reduction at the magnetic compensation, explaining the behavior of the switching current density. This model also suggests that conventional SOT effective field measurements do not allow one to conclude whether the spins are transferred to one sublattice or just simply to the net magnetization. The effective spin Hall angle measurement shows an enhancement of the spin Hall angle with the Tb concentration which suggests an additional SOT contribution from the rare earth Tb atoms.

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“…Before we study the LLB model, the LLG equation is widely used to qualitatively explain experimental findings in FiMs. As the FiM consists of antiferromagnetic coupled TM and RE sublattices, it is straightforward to apply one LLG equation to one sublattice 19 aṡ…”

Section: Appendix A: Numerical Simulation Of Fim Using the Llg Modelmentioning

confidence: 99%

Damping-like spin-orbit-torque-induced magnetization dynamics in ferrimagnets based on Landau-Lifshitz-Bloch equation

Zhu

Fong

Liang

2018

Journal of Applied Physics

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A theoretical model based on the Landau-Lifshitz-Bloch equation is developed to study the spintorque effect in ferrimagnets. Experimental findings, such as the temperature dependence, the peak in spin torque, and the angular-momentum compensation, can be well captured. In contrast to the ferromagnet system, the switching trajectory in ferrimagnets is found to be precession free. The two sublattices are not always collinear, which produces large exchange field affecting the magnetization dynamics. The study of material composition shows the existence of an oscillation region at intermediate current density, induced by the nondeterministic switching. Compared to the Landau-Lifshitz-Gilbert model, our developed model based on the Landau-Lifshitz-Bloch equation enables the systematic study of spin-torque effect and the evaluation of ferrimagnet-based devices.

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Micromagnetic simulation of exchange coupled ferri-/ferromagnetic heterostructures

Cited by 22 publications

References 26 publications

Anomalous Current-Induced Spin Torques in Ferrimagnets near Compensation

Anomalous Current-Induced Spin Torques in Ferrimagnets near Compensation

Spin-orbit torque-induced switching in ferrimagnetic alloys: Experiments and modeling

Damping-like spin-orbit-torque-induced magnetization dynamics in ferrimagnets based on Landau-Lifshitz-Bloch equation

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