Electron spin relaxation near a micron-size ferromagnet

Abstract

The behavior of small ensembles of unpaired electron spins in silica near a micrometer-size ferromagnetic tip was studied using magnetic resonance force microscopy. Signals from as few as 100 net spins within a 20 nm thick resonant slice were studied using a cantilever-driven spin manipulation protocol and a magnetic field gradient greater than 105 T/m. The spin-lattice relaxation rate was found to increase by six times within 800 nm of the ferromagnet, while no effect due to silica surface proximity was detected. The interpretion of the results was done in terms of Larmor-frequency magnetic field fluctuations emanating from the ferromagnet.