Low-frequency magnetic noise in magnetic tunnel junctions

Abstract

We studied low-frequency noise in $\mathrm{NiFe}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}\ensuremath{-}\mathrm{NiFe}$ based magnetic tunnel junctions (MTJ's) with and without a hard-axis bias field. The $1/f$ noise is observed to be magnetic-field dependent and reduced with the application of hard-axis bias fields, attributed to thermally activated magnetization fluctuations in the magnetic electrodes. A linear dependence of noise on derivative of magnetoresistance has been observed, and the magnetic-field noise for MTJ sensing elements is defined and evaluated to be as low as 60 nT $\ensuremath{\mu}\mathrm{m}/{\mathrm{Hz}}^{1/2}.$