Magnetic small-angle neutron scattering

Abstract

Small-angle neutron scattering (SANS) is one of the most important techniques for microstructure determination, being utilized in a wide range of scientific disciplines, such as materials science, physics, chemistry, and biology. The reason for its great significance is that conventional SANS is probably the only method capable of probing structural inhomogeneities in the bulk of materials on a mesoscopic real-space length scale, from roughly 1 − 300 nm. Moreover, the exploitation of the spin degree of freedom of the neutron provides SANS with a unique sensitivity to study magnetism and magnetic materials at the nanoscale. As such, magnetic SANS ideally complements more real-space and surface-sensitive magnetic imaging techniques, e.g., Lorentz transmission electron microscopy, electron holography, magnetic force microscopy, Kerr microscopy, or spinpolarized scanning tunneling microscopy. In this review article we summarize the recent applications of the SANS method to study magnetism and magnetic materials. This includes a wide range of materials classes, from nanomagnetic systems such as soft magnetic Fe-based nanocomposites, hard magnetic Nd−Fe−B-based permanent magnets, magnetic steels, ferrofluids, nanoparticles, and magnetic oxides, to more fundamental open issues in contemporary condensed matter physics such as skyrmion crystals, noncollinar magnetic structures in noncentrosymmetric compounds, magnetic/electronic phase separation, and vortex lattices in type-II superconductors. Special attention is paid not only to the vast variety of magnetic materials and problems where SANS has provided direct insight, but also to the enormous progress made regarding the micromagnetic simulation of magnetic neutron scattering.

Broken time-reversal symmetry in the topological superconductor UPt3

“…Here λ ab and ξ ab are respectively penetration depth and coherence length in the screening current plane (ab-plane), and c is a constant of order unity (typically between 1 4 and 2)) [1]. Previous SANS measurements yielded a penetration depth λ ab = 680 nm [2], and consequently (λ ab Q) 2 1 for the entire range of applied magnetic fields in this work.…”

“…Topological properties of materials are of fundamental as well as practical importance, and are currently the focus of intense research [1]. Recently, topological superconductors have received increased attention, as it was realized that vortices in them can host Majorana fermions with potential use in quantum computing [2][3][4].…”

Universal behavior of the intermediate mixed state domain formation in superconducting niobium

“…The VLcorrelation length is then defined as ξ V L = (2π)/(∆q) The Bragg peak positions are defined by the VL arrangement (structure factor). The scattering intensity depends on the local field distribution of the single vortices (form factor), which is q-and temperature dependent [41]. In the IMS, the intensity depends further on the reduced area of SS regions, while the peaks broaden due to the finite size of VL domains.…”

Structural studies of metastable and equilibrium vortex lattice domains in MgB2

“…SANS measurements [17] were performed on the CG2 General Purpose SANS beam line at the High Flux Isotope Reactor at Oak Ridge National Laboratory [18], and the D33 beam line at Institut Laue-Langevin. The final data presented in this study was collected at D33 [19][20][21] but consistent results were found at both facilities.…”