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Publication Citation: High-frequency noise measurements in spin-valve Devices

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Author(s): N. A. Stutzke; S. L. Burkett; Stephen E. Russek;
Title: High-frequency noise measurements in spin-valve Devices
Published: July 01, 2003
Abstract: High-frequency magnetic noise in magnetoresistive devices being developed for read-sensor and magnetic random access memory applications may present fundamental limitations on the performance of sub-micrometer magnetic devices. High- frequency magnetic noise (HFN) arises from intrinsic thermal fluctuations of the device magnetization. High-frequency noise spectroscopy provides a powerful tool to characterize the dynamics and response of small multilayer magnetic devices. In this study, the noise characteristics of micrometer-dimension spinvalves have been investigated at frequencies in the range of 0.1-6 GHz. At frequencies below this range 1/f noise dominates. HFN measurements, as a function of t bias current and longitudinal magnetic field are obtained for IrMn exchange-biased spin valves using a 50 GHz spectrum analyzer, low-noise amplifier, and a microwave probing system. The magnetic noise is obtained by taking the difference between the noise spectrum of the device in a saturated and unsaturated state. The data can be fit to simple models that predict the noise power to be proportional to the imaginary part of the free-layer magnetic susceptibility. There are some important differences between the high-frequency noise measurements and direct measurements of the device susceptibility (both at the device and wafer level). The noise measurements show a smaller damping parameter (a smaller ferromagnetic resonance linewidth) and additional features due to the presence of nonuniform modes.
Citation: Journal of Vacuum Science and Technology B
Volume: 21
Issue: 4
Pages: pp. 1167 - 1171
Keywords: ferromagnetic resonance,GMR,magnetic noise,spinvalves
Research Areas: Electromagnetics
PDF version: PDF Document Click here to retrieve PDF version of paper (158KB)