Thermal magnetization noise in spin valves

Thermal magnetization fluctuations (mag-noise) in giant magnetoresistive (GMR) spin valve (or any MR) heads will serve as a fundamental limit on their signal-to-noise-ratio (SNR). Measured mag-noise in several varied spin-valve read sensors is shown to be in good quantitative agreement with predictions based on the fluctuation-dissipation theorem. The dependence of magnoise and head-SNR on sensor geometry and other device parametrics is discussed.