Dynamics of Magnetic Nanoparticles Studied by Neutron Scattering

Abstract

We present the first triple-axis neutron scattering measurements of magnetic fluctuations in nanoparticles using an antiferromagnetic reflection. Both the superparamagnetic relaxation and precession modes in $\ensuremath{\sim}15\mathrm{nm}$ hematite particles are observed. The results have been consistently analyzed on the basis of a simple model with uniaxial anisotropy and the N\'eel-Brown theory for the relaxation.