The Magnetic Structure of NiFe2O4 Nanoparticles

Abstract

The Mössbauer studies of the magnetic structure of nickel ferrite (NiFe₂O₄) nanoparticles (NPs) are presented. It is shown that the redistribution of ions over nonequivalent crystallographic positions occurs upon a decrease in the size of NiFe₂O₄ crystallites to nanovalues, thus leading to the structural transformation of NiFe₂O₄ nanoparticles from inverse spinel to mixed spinel. It has been established that the magnetic moments of Fe ions in the volume of NiFe₂O₄ nanoparticles are ferromagnetically (collinearly) ordered, being noncollinear (or oblique) in the near-surface layer probably due to the frustration of moments in the near-surface layer of nanoparticles.