Experimental observation of third-order effect in magnetic small-angle neutron scattering

TL;DR

This paper experimentally and numerically demonstrates a third-order effect in magnetic small-angle neutron scattering, confirming recent theoretical predictions and extending the model to complex defect profiles for quantitative analysis.

Contribution

It provides the first experimental observation of the third-order effect in magnetic SANS and extends the theoretical model to arbitrary defect profiles.

Findings

Third-order effect observed experimentally in magnetic SANS.

Numerical simulations confirm the theoretical prediction.

Extended model describes experimental data quantitatively.

Abstract

A recent theory [Metlov and Michels, Phys. Rev. B 91, 054404 (2015)] predicts a qualitatively new effect in the magnetic small-angle neutron scattering (SANS) cross section of statistically-isotropic disordered ferromagnetic media. The effect is due to the third-order terms in the amplitude of the inhomogeneities. Here, its existence is demonstrated both numerically via large-scale micromagnetic simulations and analyzed experimentally in a two-phase iron-based nanocomposite. The previous model is extended to an arbitrary spatial defect profile, which allows us to describe the experimental field dependence of the third-order SANS effect quantitatively.