Soft X-ray magnetic scattering studies of 3D magnetic morphology along buried interfaces in NiFe/CoPd/NiFe nanostructures

Abstract

With the continuing interest in new magnetic materials for sensor devices and data storage applications, the community needs reliable and sensitive tools for the characterization of such materials. Soft X-rays tuned to elemental absorption edges are a depth and element sensitive probe of magnetic structure at the nanoscale, and scattering measurements have the potential to provide 3D magnetic structural information of the material. In this work we develop a methodology in transmission geometry that allows one to probe the spatial distribution of the magnetization along the different layers of magnetic heterostructures. We study the in-plane/out-of-plane transition of magnetic domains in multilayer thin film systems consisting of two layers of NiFe top and bottom, and a 50 repeat Co/Pd multilayer in the centre. The experimental data are analysed by simulating scattering data starting from micromagnetic simulations, and we find that the out of plane domains of the Co/Pd multilayer intrude into the NiFe layers to a greater extent than would be expected from micromagnetic simulations performed using the standard magnetically isotropic input parameters for the NiFe layers.

General treatment of off-specular resonant soft x-ray magnetic scattering using the distorted-wave Born approximation: Numerical algorithm and experimental studies with hybrid chiral domain structures

“…During the transmission through the sample before and after a reflection event, it is also likely that there are further losses not accounted for by the imaginary part of the refractive index due to diffuse scattering from grain boundaries. Such diffuse scattering was observed in previous work [6,25], and is of increasing importance as the incidence angle approaches 90 degrees (as measured from the normal). The magnitude of this effect is expected to depend on photon energy, angle of incidence, and specific sample fabrication characteristics; and we are of the opinion that a full investigation of this factor is warranted.…”

“…Over the past 20 years, the field of resonant elastic soft X-ray scattering has widely expanded into a standard tool for the nanometer resolution characterization of magnetic domains in thin film samples [1][2][3][4][5][6][7][8]. However, an important gap in the literature is the lack of a standard protocol for the modelling of resonant scattering, which has limited the degree to which quantitative conclusions may be extracted from experimental data.…”

“…The algorithm presented in this manuscript was developed and improved through the task of analysing experimental data, some of which has already been published [23] or will be soon submitted for publication [22,24], and is an extension of previous transmission geometry work [6,25]. The experimental material included was specifically chosen to test certain hypotheses which arose from the analysis of the data to be published in [22], namely the ability to quantitatively determine the depth of the Bloch part of the domain wall -a feature believed to be related to the value of the Dzyaloshinskii-Moriya interaction (DMI) [17], and qualitatively explored by Zhang et al [26].…”

“…This should be defined over the planes of each interface in the multilayer sample due to the physical significance of each interface. It is ideal in this step to use micromagnetic simulations in order to provide a physical basis to the model chosen, with a method for extrapolating a localized micromagnetic simulation over the up to several hundred micrometre size of a typical X-ray scattering experiment published previously in [6,25,47]. It is alternatively possible to define the magnetization distribution in geometric terms of average domain width, domain wall width and domain wall angle varying between 0 for Bloch and π/2 for Néel.…”

Revealing 3D magnetization of thin films with soft X-ray tomography: magnetic singularities and topological charges

“…In the soft X-ray range, reflection and transmission experiments have reported interesting results [10][11][12][13][14] . X-ray magnetic scattering has allowed a detailed characterization of skyrmions in periodic arrays 10,11 and of periodic striped domains in NiFe/CoPd multilayers 12 . In transmission, two-dimensional (2D) magnetization patterns have been extracted from tubular samples acquired at different angles 13 .…”