Figure 1

Hysteresis loop of MTJ conductance $G$ versus in-plane magnetic field $H_x$ measured under $\pm 80\mathrm{mV}$ direct voltage bias $V_{\mathrm{dc}}$. The left inset shows schematic of the MTJ nanopillar. The right inset displays variation of the effective perpendicular anisotropy field $\Delta H_p(V_{\mathrm{dc}})$ with DC voltage extracted from the $G(H_x)$ hysteresis loops via Eq. (2) (squares) and a linear fit to the data (line).Reuse & Permissions

Figure 2

Rectified voltage $V_{\mathrm{mix}}$ versus frequency $f$ of the applied microwave signal measured at several values of the in-plane magnetic field $H_x$. The FMR response curves $V_{\mathrm{mix}}(f)$ at different fields are vertically offset by 0.06 mV. At $H_x=0$, $V_{\mathrm{mix}}(f)$ is a symmetric Lorentzian curve, while at $|H_x|>0$, $V_{\mathrm{mix}}(f)$ is a sum of symmetric and antisymmetric Lorentzians. The antisymmetric part of $V_{\mathrm{mix}}(f)$ changes sign upon reversal of $H_x$, while the symmetric part is negative for any $H_x$.Reuse & Permissions

Figure 3

Macrospin simulations of ST-FMR line shape assuming nonzero in-plane ST and (a) nonzero VCMA ($\Delta H_{\perp }=4\mathrm{Oe}$) and zero fieldlike ST ($b_f=0$), (b) zero VCMA ($\Delta H_{\perp }=0\mathrm{Oe}$) and nonzero fieldlike ST ($b_f=0.5$). The curves for different values of $H_x$ are vertically offset by 0.06 mV.Reuse & Permissions

Figure 4

Macrospin simulations of ST-FMR response curves with (a) zero ($H_{\perp 1}=0$) and (b) positive ($H_{\perp 1}=280\mathrm{Oe}$) second-order perpendicular anisotropy. The curves are vertically offset by 0.06 mV. (c) Macrospin and micromagnetic simulations of ST-FMR resonance frequency versus $H_x$ for zero and positive $H_{\perp 1}$ (lines) shown together with the experimental data (solid squares). (d) Macrospin and micromagnetic simulations (lines) of the $G(H_x)$ hysteresis loop using the magnetic anisotropy parameters given by the best fits in (c). Squares are experimental data measured at zero bias voltage. (e) Sensitivity of the MTJ to a microwave signal is enhanced by VCMA when the free layer magnetization is tilted from the sample normal by magnetic field $H_x=+40\mathrm{Oe}$.Reuse & Permissions