Reduced spin torque nano-oscillator linewidth using He+ irradiation

Abstract

We use He + irradiation to tune the nonlinearity, N , of all-perpendicular spin-torque nanooscillators (STNOs) using the He + fluence-dependent perpendicular magnetic anisotropy (PMA) of the [Co/Ni] free layer. Employing fluences from 6 to 20×10 14 He + /cm 2 , we are able to tune N in an in-plane field from strongly positive to moderately negative. As the STNO microwave signal properties are mainly governed by N , we can in this way directly control the threshold current, the current tunability of the frequency, and the STNO linewidth. In particular, we can dramatically improve the latter by more than two orders of magnitude. Our results are in good agreement with the theory for nonlinear auto-oscillators, confirm theoretical predictions of the role of nonlinearity, and demonstrate a straightforward path towards improving the microwave properties of STNOs. DOI: XXXXXX.Spin-torque nano-oscillators (STNOs) are among the most promising candidates for nanoscale broadband microwave generators [1-6] and detectors [7][8][9]. STNOs can generate broadband microwave frequencies ranging from hundreds of MHz to the sub-THz [10-12], controlled by both magnetic fields and dc currents [5,13]. Moreover, the device size can be reduced to a few tens of nanometers, which is of great opportunity for industrial applications. They can also host a range of novel magnetodynamical spin wave modes, such as propagating spin waves of different orders [14,15], and magnetodynamical solitons, such as spin wave bullets [14] and droplets [3].

Radio-Frequency Multiply-and-Accumulate Operations with Spintronic Synapses

“…To quantify this effect, we choose parameters extracted from experiments on similar structures as the resonators. We take nonlinear coefficients N=0.1 and Q=1 close to values determined experimentally in studies of spin-torque nano-oscillators [29,[34][35][36]. We chose frequencies close to 200 MHz, parameters 𝛽 = 1.7 × 10 6 C -1 and 𝛾 = 7.1 × 10 7 Hz.W -1/2 according to experimental values from prior work [34].…”

Femtosecond laser driven precessing magnetic gratings

“…The precession frequency increases with the external field following the expected trend from simulated ferromagnetic resonance (FMR, black dashed line) frequency. 38 The discrepancy between the experimental and calculated results may tentatively be attributed to the inhomogeneous demagnetization (shown in Fig. 3I) and the different precession angles (shown in Fig.…”

Applications of nanomagnets as dynamical systems: II

“…An intriguing analog application of nanomagnets is in microwave oscillators [32][33][34][35][36]. Oscillators are very important passive components of electronic circuits.…”