Charge pumping and the colored thermal voltage noise in spin valves

Jiang Xiao, Gerrit E. W. Bauer, Sadamichi Maekawa, Arne Brataas

Published 2009-02-13, updated 2009-04-29Version 2

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.