Polarized Neutron Reflectivity and Scattering from Magnetic Nanostructures and Spintronic Materials

Abstract

Polarized neutron reflectivity and scattering has established itself as one of the most important experimental methods for the analysis of magnetic nanostructures and spintronic materials. With this method, seminal contributions have been made to the physics of thin magnetic films, interfaces, and superlattices, including collinear and noncollinear exchange coupling. Another rich area is the exchange coupling phenomena between ferromagnetic and antiferromagnetic layers. Presently neutron scattering from laterally patterned magnetic arrays has become very active for the understanding of domain structures, domain reversals, and correlation effects. Established more than 25 years ago, polarized neutron reflectivity was focused mainly on the specularly reflected intensity. With the advent of area detectors and efficient wide‐angle spin analyzers, the off‐specular diffuse scattering could be analyzed, contributing to a more complete picture of the physics of magnetic nanostructures and patterned arrays. In this review a basic introduction into the fundamentals of polarized neutron reflectivity is provided, including specular and off‐specular scattering. For the description of the off‐specular part, the distorted wave Born approximation has rigorously been applied and features missed in the simpler Born approximation are pointed out. The methods are illustrated by a number of examples from research into magnetic thin films, spin valves, magnetic multilayers, exchange bias systems, spintronic materials, and periodic magnetic arrays of islands and stripes.

Reversible electric-field control of magnetization at oxide interfaces

“…In contrast, for the top layer, a reduction of the magnitude of the magnetization vector together ( Supplementary Fig. 2) with gradual rotation is observed, indicating that the magnetization switches via a combination of coherent rotation and formation of small domains 22 . The distinction between large and small domains is determined relative to the longitudinal projection of the coherence length (L) of the neutron beam on the sample during the PNR experiments.…”

Domain-wall structure in thin films with perpendicular anisotropy: Magnetic force microscopy and polarized neutron reflectometry study

“…In contrast with other magnetic measurement techniques which provide volume-averaged information, PNR gives depth and lateral resolution for both the nuclear and the magnetic density distribution in the sample [31][32][33], allowing determination of the magnetization amplitude and direction in each layer, even when the magnetic layer is buried in a multilayer stack. Although PNR is only sensitive to in-plane magnetization [34], we will show that the domain-wall structure in materials with perpendicular anisotropy can be determined. Thin films of CoCrPt, an alloy which has received significant attention for perpendicular magnetic recording media [35,36], were studied.…”

Magnetization and magnetization reversal in epitaxial Fe/Cr/Co asymmetric spin-valve systems

“…The experimental result is represented in intensity maps plotted over the incident angle α i and exit angle α f of the neutrons with respect to the sample surface and for both incident spin states (up or down) (see Fig. 7) together with theoretical simulations carried out in the distorted wave Born approximation (DWBA) 36 for scattering from magnetic interfacial roughness. The high-intensity ridge running along the diagonal α f = α i is the specular reflectivity.…”