Preparation and Magnetic Properties of Small NiFe₂O₄ Particles

Abstract

NiFe₂O₄ small particles (in the few hundred angstrom size range and up) have been prepared by a chemical precipitation method and subsequent heat treatments, and their magnetic properties have been explored in particular reference to their magnetic structure for its smallness of the particle size. The magnetic moment at low temperatures is appreciably lower than the value reported for bulk material. Mossbauer spectra, obtained with a longitudinal high magnetic field applied, unambiguously establish that a non-collinear structure exists that is most pronounced for the smallest particles. The analysis indicates that a surface effect of the crystallites which make up a particle is the origin of this phenomenon.