On the angular anisotropy of the randomly-averaged magnetic neutron scattering cross section of nanoparticles

TL;DR

This paper investigates how the magnetic small-angle neutron scattering (SANS) pattern of nanoparticles varies with magnetic anisotropy and particle properties, revealing anisotropic signals even in demagnetized states.

Contribution

It introduces a calculation of the magnetic SANS cross section for randomly-oriented, uniformly magnetized nanoparticles considering various anisotropy symmetries and particle inhomogeneities.

Findings

Anisotropic magnetic SANS patterns can occur in demagnetized states.

Magnetic anisotropy symmetry influences the SANS pattern shape.

Particle size distribution and correlations affect the scattering signal.

Abstract

We calculate the magnetic SANS cross section of dilute ensembles of uniformly magnetized and randomly-oriented Stoner-Wohlfarth particles using the Landau-Lifshitz equation. The focus of our study is on the angular anisotropy of the magnetic SANS signal as it can be seen on a two-dimensional position-sensitive detector. Depending on the symmetry of the magnetic anisotropy of the particles (e.g. uniaxial, cubic), an anisotropic magnetic SANS pattern may result, even in the demagnetized state or at the coercive field. The case of inhomogeneously magnetized particles and the effects of a particle-size distribution and interparticle correlations are discussed.