Low-non-linearity spin-torque oscillations driven by ferromagnetic nanocontacts

Abstract

Spin-torque oscillators are strong candidates as nano-scale microwave generators and detectors. However, because of large amplitude-phase coupling (non-linearity), phase noise is enhanced over other linear auto-oscillators. One way to reduce nonlinearity is to use ferromagnetic layers as a resonator and excite them at localized spots, making a resonator-excitor pair. We investigated the excitation of oscillations in dipole-coupled ferromagnetic layers, driven by localized current at ferromagnetic nano-contacts. Oscillations possessed properties of optical-mode spin-waves and at low field ($\approx$200 Oe) had high frequency (15 GHz), a moderate precession amplitude (2--3${}^{\circ }$), and a narrow spectral linewidth ($<$3 MHz) due to localized excitation at nano-contacts. Micromagnetic simulation showed emission of resonator's characteristic optical-mode spin-waves from disturbances generated by domain-wall oscillations at nano-contacts.

References in corpus (8)

• Bias-driven large power microwave emission from MgO-based tunnel magnetoresistance devices
• Generation linewidth of an auto-oscillator with a nonlinear frequency shift: Spin-torque nano-oscillator
• Coupling efficiency for phase locking of a spin transfer oscillator to a microwave current
• Temperature dependence of nonlinear auto-oscillator linewidths: Application to spin-torque nano-oscillators
• Direct experimental measurement of phase-amplitude coupling in spin torque oscillators
• Amplitude-Phase Coupling in a Spin-Torque Nano-Oscillator
• Current-perpendicular-to-plane magnetoresistance of a domain wall confined in a nano-oxide-layer
• Formation and anisotropic magnetoresistance of Co/Pt nano-contacts through aluminum oxide barrier

Cited by in corpus (1)

• Switching based Spin Transfer Torque Oscillator with zero-bias field and large tuning-ratio