Charge pumping and the colored thermal voltage noise in spin valves

TL;DR

This paper investigates how spin pumping and thermal magnetization fluctuations generate voltage noise in spin valves, revealing that noise characteristics depend on magnetization states and can serve as an alternative measurement method.

Contribution

It introduces the concept of colored thermal voltage noise in spin valves caused by magnetization fluctuations, offering a new approach to study ferromagnetic resonance without traditional FMR experiments.

Findings

Voltage noise exhibits absorption lines at FMR and zero frequency.

Thermal voltage noise can be comparable to Johnson-Nyquist noise.

Measurement of voltage noise provides an alternative to FMR for nanoscale ferromagnetic circuits.

Abstract

Spin pumping by a moving magnetization gives rise to an electric voltage over a spin valve. Thermal fluctuations of the magnetization manifest themselves as increased thermal voltage noise with absorption lines at the ferromagnetic resonance frequency and/or zero frequency. The effect depends on the magnetization configuration and can be of the same order of magnitude as the Johnson-Nyquist thermal noise. Measuring colored voltage noise is an alternative to ferromagnetic resonance experiments for nano-scale ferromagnetic circuits.