The antisymmetric Dzyaloshinskii-Moriya interaction (DMI) plays a decisive role for the stabilization and control of chirality of skyrmion textures in various magnetic systems exhibiting a noncentrosymmetric crystal structure. A less studied aspect of the DMI is that this interaction is believed to be operative in the vicinity of lattice imperfections in crystalline magnetic materials, due to the local structural inversion symmetry breaking. If this scenario leads to an effect of sizable magnitude, it implies that the DMI introduces chirality into a very large class of magnetic materialsdefect-rich systems such as polycrystalline magnets. Here, we show experimentally that the microstructural-defect-induced DMI gives rise to a polarization-dependent asymmetric term in the small-angle neutron scattering (SANS) cross section of polycrystalline ferromagnets with a centrosymmetric crystal structure. The results are supported by theoretical predictions using the continuum theory of micromagnetics.This effect, conjectured already by Arrott in 1963, is demonstrated for nanocrystalline terbium and holmium (with a large grain-boundary density), and for mechanicallydeformed microcrystalline cobalt (with a large dislocation density). Analysis of the scattering asymmetry allows one to determine the defect-induced DMI constant, D = 0.45 ± 0.07 mJ/m 2 for Tb at 100 K. Our study proves the generic relevance of the DMI for the magnetic microstructure of defect-rich ferromagnets with vanishing intrinsic DMI. Polarized SANS is decisive for disclosing the signature of the defectinduced DMI, which is related to the unique dependence of the polarized SANS cross section on the chiral interactions. The findings open up the way to study defectinduced skyrmionic magnetization textures in disordered materials.

Magnetic nanoparticles offer unique potential for various technological, biomedical, or environmental applications thanks to the size-, shape- and material-dependent tunability of their magnetic properties. To optimize particles for a specific...

We report the results of an unpolarized small-angle neutron scattering (SANS) study on Mn-Zn ferrite (MZFO) magnetic nanoparticles with the aim to elucidate the interplay between their particle size and the magnetization configuration. We study different samples of single-crystalline MZFO nanoparticles with average diameters ranging between 8 to 80 nm, and demonstrate that the smallest particles are homogeneously magnetized. However, with increasing nanoparticle size, we observe the transition from a uniform to a nonuniform magnetization state. Field-dependent results for the correlation function confirm that the internal spin disorder is suppressed with increasing field strength. The experimental SANS data are supported by the results of micromagnetic simulations, which confirm an increasing inhomogeneity of the magnetization profile of the nanoparticle with increasing size. The results presented demonstrate the unique ability of SANS to detect even very small deviations of the magnetization state from the homogeneous one.

Shell ferromagnetism is a new functional property of certain Heusler alloys which was recently observed in Ni 50 Mn 45 In 5 . We report the results of a comparative study of the magnetic microstructure of bulk Ni 50 Mn 45 In 5 Heusler alloys using magnetometry, synchrotron x-ray diffraction, and magnetic small-angle neutron scattering (SANS). By combining unpolarized and spin-polarized SANS (so-called POLARIS) we demonstrate that a number of important conclusions regarding the mesoscopic spin structure can be made. In particular, the analysis of the magnetic neutron data suggests that nanoprecipitates with an effective ferromagnetic component form in an antiferromagnetic matrix on field annealing at 700 K. These particles represent sources of perturbation, which seem to give rise to magnetically disordered regions in the vicinity of the particle-matrix interface. Analysis of the spin-flip SANS cross section via the computation of the correlation function yields a value of ∼55 nm for the particle size and ∼20 nm for the size of the spin-canted region.

Spin-orbit torque (SOT)-induced magnetization switching in Co/Pt multilayer structures with a Pt buffer layer is studied aiming to realize SOT-magnetic random access memory (MRAM) devices with high thermal stability. Current-induced magnetization switching and effective fields are measured using Hall-bar devices. The switching efficiency, defined as a ratio of the areal anisotropy energy density to switching current density, increases with increasing the number of Co/Pt stacks. This trend is in accordance with the stacking number dependence of effective fields per unit current density. The effective spin-Hall angle of the Pt buffer layer for the sample with multiple Co/Pt stacks is significantly larger than that of Pt previously reported, suggesting a generation of SOT in Co/Pt multilayers. These results indicate that Co/Pt multilayers are promising for SOT-MRAM devices possessing high thermal stability and small switching current.