Nonhysteretic Vortex Magnetic Tunnel Junction Sensor with High Dynamic Reserve

Multiple geometrical conditions for different magnetic vortex states to appear in micrometer-sized magnetic tunnel junctions (MTJs) are investigated in experiment and simulation. Both results match up well, providing clear images of vortex behaviors. We pattern a compact array of single-vortex MTJ elements and perform magnetotransport and noise measurements. This sensor features nonhysteretic behavior, a small size of 0.5 \ifmmode\times\else\texttimes\fi{} 0.5 ${\mathrm{mm}}^{2}$, a low normalized noise of ${10}^{\ensuremath{-}13}\phantom{\rule{0.25em}{0ex}}{\mathrm{Hz}}^{\ensuremath{-}1}$, a detectability of $18\phantom{\rule{0.1em}{0ex}}nT/\sqrt{Hz}$ at 1 Hz, and a large dynamic range of 100 Oe. Its 115 dB broad dynamic reserve and superior stability against temperature and environmental stray fields are ideally suited for magnetic sensing applications.