Unveiling the anisotropic fractal magnetic domain structure in bulk crystal of antiskyrmion-host (Fe,Ni,Pd)$_3$P by small-angle neutron scattering

TL;DR

This study uses small-angle neutron scattering and magnetic force microscopy to reveal the anisotropic fractal nature of magnetic domain structures in bulk antiskyrmion-hosting crystals, showing temperature and field-dependent changes.

Contribution

It provides the first quantitative analysis of fractal magnetic domain structures in bulk antiskyrmion materials using SANS, highlighting their anisotropic and temperature-dependent properties.

Findings

Magnetic domains exhibit anisotropic fractal structures at mesoscopic scales.

Fractal features diminish with increasing magnetic field.

Temperature influences the anisotropy and fractal characteristics of the domains.

Abstract

Intermetallic Pd-doped (Fe,Ni)$_3$P, that crystalizes in a non-centrosymmetric tetragonal structure with $S_4$ symmetry, has recently been discovered to host magnetic antiskyrmions, antivortex-like topological spin textures. In this material, uniaxial magnetic anisotropy and dipolar interactions play a significant role, giving rise to finely branched magnetic domain patterns near the surface of bulk crystals, as revealed by a previous magnetic force microscopy (MFM) measurement. However, small-angle neutron scattering (SANS) is a more suitable method for characterizing bulk properties and fractal structures at the mesoscopic length scale. In this study, using SANS and MFM, we quantitatively investigate the magnetic domain structure in bulk single crystals of (Fe$_{0.63}$Ni$_{0.30}$Pd$_{0.07}$)$_3$P. The SANS results demonstrate that the magnetic domain structure exhibits anisotropic fractal character on the length scale down to the width of the magnetic domain walls. The fractal features are gradually lost in magnetic fields, and different field dependences are observed at 300 K and 2 K due to a temperature-dependent anisotropy. This study quantifies the fractality of the highly anisotropic magnetic domain structures in an antiskyrmion material, and highlights the versatility of SANS for the study of fractal structures in magnetic systems.