Magnetic Dissipation and Fluctuations in Individual Nanomagnets Measured by Ultrasensitive Cantilever Magnetometry

Abstract

Cantilever magnetometry with moment resolution better than ${10}^4{\mu }_B$ was used to study individual nanomagnets. By using the fluctuation-dissipation theorem to interpret measurements of field-induced cantilever damping, the low frequency spectral density of magnetic fluctuations could be determined with resolution better than $1{\mu }_B{\mathrm{Hz}}^{-1\mathrm{}/2}$. Cobalt nanowires exhibited significant magnetic dissipation and the associated magnetic fluctuations were found to have $1/f$ frequency dependence. In individual submicron rare-earth alloy magnets, the dissipation/fluctuation was very small and not distinguishable from that of a bare silicon cantilever.