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Analysis of the Noise Spectra from Oxidized Superparamagnetic Nanoparticles



Solomon I. Woods, Snorri Ingvarsson, Shouheng Sun, John Kirtley


Expressions for the thermal noise from a collection of exchange-biased magnetic nanoparticles are derived and used to analyze the magnetic noise from thin films of partially oxidized nanoparticles. Functionalized Co nanoparticles with diameters between 3 nm and 6 nm were oxygenated in solution and then deposited on oxidized silicon substrates, self-assembling into arrays of magnetic nanoparticles during solvent evaporation. Magnetization measurements exhibited the development of exchange bias with oxygenation as evidenced by an increasing exchange field and coercivity. Noise measurements of the exchanged-biased nanoparticles using a micro-SQUID sensor are shown to be consistent with theoretical expectations and are used to extract the magnetic energy distributions of the Co/CoO nanoparticles.
Physical Review B


nanoparticles, magnetic anisotropy, superparamagnetism, magnetic noise, micro-SQUID


Woods, S. , Ingvarsson, S. , Sun, S. and Kirtley, J. (2014), Analysis of the Noise Spectra from Oxidized Superparamagnetic Nanoparticles, Physical Review B, [online], (Accessed April 17, 2024)
Created August 18, 2014, Updated February 19, 2017