Unraveling the magnetic softness in Fe-Ni-B based nanocrystalline material by magnetic small-angle neutron scattering

TL;DR

This study uses magnetic small-angle neutron scattering to analyze magnetic interactions and anisotropy in Fe-Ni-B nanocrystalline alloy, revealing insights into magnetic softness and interaction parameters.

Contribution

It introduces a detailed neutron scattering analysis combined with micromagnetic theory to understand magnetic interactions in Fe-Ni-B nanocrystalline materials.

Findings

Significant spin-misalignment scattering related to particle-matrix interfaces.

Field dependence explained by micromagnetic small-angle neutron scattering theory.

Access to magnetic interaction parameters like exchange-stiffness constant.

Abstract

We employ magnetic small-angle neutron scattering to investigate the magnetic interactions in $(Fe_{0.7}Ni_{0.3})_{86}B_{14}$ alloy, a HiB-NANOPERM-type soft magnetic nanocrystalline material, which exhibits an ultrafine microstructure with an average grain size below 10 nm. The neutron data reveal a significant spin-misalignment scattering, which is mainly related to the jump of the longitudinal magnetization at internal particle-matrix interfaces. The field dependence of the neutron data can be well described by the micromagnetic small-angle neutron scattering theory. In particular, the theory explains the 'clover-leaf-type' angular anisotropy observed in the purely magnetic neutron scattering cross section. The presented neutron-data analysis also provides access to the magnetic interaction parameters, such as the exchange-stiffness constant, which plays a crucial role towards the optimization of the magnetic softness of Fe-based nanocrystalline materials.