Room temperature giant magnetoresistance detection of spin hall nano-oscillator dynamics in synthetic antiferromagnetic Spin-Valve

TL;DR

This paper introduces a synthetic antiferromagnetic spin-valve heterostructure that enables room-temperature giant magnetoresistance detection of spin Hall nano-oscillator dynamics, overcoming power limitations of conventional devices.

Contribution

The work demonstrates a novel SAF-SV heterostructure with high GMR ratio for efficient detection of SHNO dynamics at room temperature, with stable auto-oscillations and tunable frequencies.

Findings

Achieved GMR ratio of 0.568% in SAF-SV heterostructure.

Observed stable auto-oscillations at 0.82 mA bias current.

Demonstrated frequency tunability and dual-mode behavior.

Abstract

Conventional spin Hall nano-oscillators (SHNOs) face fundamental power limitations due to the low anisotropic magnetoresistance (AMR < 0.3%) of ferromagnetic layers. To address this, we developed a synthetic antiferromagnetic spin-valve (SAF-SV) heterostructure [Ta/NiFe/Ru/NiFe/Cu/NiFe/Hf/Pt] that enables efficient giant magnetoresistance (GMR)-based detection of SHNO dynamics at room temperature. The NiFe/Ru/NiFe SAF reference layer, operating in the spin-flop state, couples with the NiFe free layer through a Cu spacer to achieve a remarkable GMR ratio of 0.568% - exhibiting complete independence of magnetic field/current orientation. Spin-torque ferromagnetic resonance (ST-FMR) verifies that the ferromagnetic resonance linewidth of the free layer can be effectively modulated by dc current through the Pt heavy metal layer, while maintaining decoupled dynamics from the SAF layer. Thermal management via high-thermal-conductivity SiC substrates and AlN capping layers successfully mitigates current-shunting-induced Joule heating. Notably, stable auto-oscillation peaks are observed at 0.82 mA bias current, with oscillation frequency tunable by external magnetic field and potential dual-mode behavior at low fields. This work establishes a new paradigm for room-temperature, high-power spintronic oscillators, offering significant potential for neuromorphic computing and coherent RF communication applications.