Figure 1

(a) Schematic of the nanopillar device geometry. $H_{op}$ and $H_{ip}$ indicate the directions of the positive out-of-plane and in-plane magnetic fields. (b) Top view of the nanopillar before depositing the top electrode, as viewed by a scanning electron microscope. (c) Magnetization curves of a large-area multilayer sample for magnetic field applied out of plane (blue) and in plane (red). (d) Magnetoresistance curves for a nanopillar device for magnetic field applied out of plane (blue) and in plane (red) near zero current (500 μA). The dotted curves are scans from the positive to the negative field and the solid curves are the reverse scans. The black curves represent a minor loop.Reuse & Permissions

Figure 2

(a) The measured microwave PSD as a function of the current bias at zero external field. (b) The associated dc resistance.Reuse & Permissions

Figure 3

(a) The peak frequency, (b) power spectral density, and (c) linewidth for the fundamental peak A (large red circles) and the second harmonic B (small blue circles) as a function of $I_{dc}$. The upper panels in (a), (b), and (c) show the experimental data and the lower panels are the results of the micromagnetic simulations at room temperature (300 K). (d) The results of room-temperature micromagnetic simulations for the single-free-layer spin valve geometry described in the text, for the frequency and the linewidth corresponding to oscillations of the average $x$ component of the free layer magnetization.Reuse & Permissions

Figure 4

(a) Calculated power spectra for the magnetization oscillations in the top and bottom free layers and for the resistance oscillations of the full device at $I_{dc}=5.3$ mA and zero external magnetic field. (b) Time traces for the calculated average $x$ and $y$ components of the magnetization oscillations in the top ($m_t$) and bottom ($m_b$) free layers, together with the calculated resistance oscillations. The black markers on the resistance oscillation indicate the six time points $t=t_1$ to $t_6$. (d) Micromagnetic configurations for the top and bottom free layers predicted by the micromagnetic simulation for the time points $t_1$ to $t_6$. The color scale represents the $x$ component of the magnetization. The simulations in this figure correspond to zero temperature.Reuse & Permissions