Influence of MgO barrier quality on spin-transfer torque in magnetic tunnel junctions

Abstract

We studied the bias dependence of spin transfer torque in the MgO-based magnetic tunnel junction using a field-modulated spin torque ferromagnetic resonance measurement technique for three devices with tunneling magnetoresistances (MRs) of 60%, 67%, and 73%, respectively. The devices with a lower MR ratio showed the presence of multiple modes, while the device with higher MR (73%) showed a single resonance mode. We found a lower out-of-plane torkance in our devices compared to the in-plane torkance. The out-of-plane torque is linear with applied bias, while the bias dependence of in-plane torque shows a strong dependence on the MR ratio and hence the barrier quality.

Spin and charge drift-diffusion in ultra-scaled MRAM cells

“…The implementation discussed until now produces a linear dependence of the torques on the bias voltage, with a vanishing damping-like component for . Fabricated MRAM devices usually exhibit clear non-linearity in the observed bias dependence of both the torques and the TMR 29 , 30 . As a way to account for this non-linearity, bias dependence can be included in the polarization parameters and .…”

Spin and Charge Drift-Diffusion in Ultra-Scaled MRAM Cells

“…The implementation discussed until now produces a linear dependence of the torques on the bias voltage, with a vanishing damping-like component for P η RL = P η FL . Fabricated MRAM devices usually exhibit clear non-linearity in the observed bias dependence of both the torques and the TMR 28,29 . As a way to account for this non-linearity, bias dependence can be included in the polarization parameters P RL and P FL .…”

Macrospin analysis of RF excitations within fully perpendicular magnetic tunnel junctions with second order easy-axis magnetic anisotropy contribution

“…The field-like torque is generally neglected in metallic nanostructures, but in MTJs has to be taken into account and could reach an amplitude comparable to that of damping-like torque, as estimated in different theoretical and experimental papers [12,[19][20][21][22]. However, it should be mentioned that the dependence of the field-like torque on the bias voltage still needs to be clarified, as different papers report both quadratic [19][20][21] and linear [23][24][25] variation on V. eff H denotes the effective field that in the macrospin approximation accounts for the magnetic anisotropy field H u , the externally applied magnetic field H app , and the demagnetizing field H D . The demagnetizing field H D is estimated using the demagnetizing tensor ( , , )…”