Surface vacancy mediated pinning of the magnetization inγ−Fe2O3nanoparticles: A micromagnetic simulation study

Results from finite temperature sLLG simulations of an atomistic core-shell model of $\ensuremath{\gamma}\ensuremath{-}{\mathrm{Fe}}₂{\mathrm{O}}₃$ nanoparticles are presented. Radial surface anisotropy gives rise to a surface magnetization with a N\'eel-like domain wall separating the magnetic poles. It is shown that the pinning of the domain wall by the oxygen anion sites plays an important role in low temperature relaxation processes.