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 (≈200 Oe) had high frequency (15 GHz), a moderate precession amplitude (2--3∘), 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.
@article{arxiv.1503.08408,
title = {Low-non-linearity spin-torque oscillations driven by ferromagnetic nanocontacts},
author = {Muftah Al-Mahdawi and Yusuke Toda and Yohei Shiokawa and Masashi Sahashi},
journal= {arXiv preprint arXiv:1503.08408},
year = {2017}
}