TY - JOUR A1 - Smekhova, Alevtina A1 - Szyjka, Thomas A1 - La Torre, Enrico A1 - Ollefs, Katharina A1 - Eggert, Benedikt A1 - Coester, Birte A1 - Wilhelm, Fabrice A1 - Bali, Rantej A1 - Lindner, Jürgen A1 - Rogalev, A. A1 - Többens, Daniel Maria A1 - Weschke, Eugen A1 - Luo, Chen A1 - Chen, Kai A1 - Radu, Florin A1 - Schmitz-Antoniak, Carolin A1 - Wende, Heiko T1 - Irradiation-induced enhancement of Fe and Al magnetic polarizations in Fe60Al40 films JF - New Journal of Physics N2 - The rise of Fe magnetic moment, changes in Al electronic structure and a variation of Al magnetic polarization in thin films of transition metal aluminide Fe60Al40 have been probed through the order-disorder phase transition by soft X-ray absorption spectroscopy and X-ray resonant magnetic reflectivity in the extreme ultraviolet regime. In a course of the transition induced by 20 keV Ne+ irradiation with low fluences (1014 ions·cm-2), X-ray magnetic circular dichroism spectra taken at the Fe L2,3 absorption edges at room and low temperatures revealed a pronounced increase of Fe 3d states spin-polarization. X-ray resonant magnetic reflectivity applied to the Al L2,3 and Fe M2,3 edges allowed to detect the magnetic polarization of Al atoms in the films. The changes in Al electronic structure have been seen by alteration of Al K edge X-ray absorption near edge structure. A difference in anisotropy fields for films before and after irradiation has been observed by element-specific hysteresis loops recorded at low temperatures in absorption and reflection geometries at the Fe L2,3 and M2,3 edges, respectively. An attempt to reduce the top oxide layer by an inductively coupled hydrogen plasma has shown a possibility to recover the chemically ordered phase. KW - chemical disorder KW - ion-irradiation KW - XANES KW - XMCD KW - plasma treatment Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-18381 SN - 1367-2630 VL - 26 PB - Institute of Physics Publishing (IOP) ER - TY - JOUR A1 - Shams, S. Fatemeh A1 - Schmitz, Detlef A1 - Smekhova, Alevtina A1 - Ghazanfari, Mohammad Reza A1 - Giesen, Margret A1 - Weschke, Eugen A1 - Chen, Kai A1 - Luo, Chen A1 - Radu, Florin A1 - Schmitz-Antoniak, Carolin T1 - Element-specific contributions to improved magnetic heating of theranostic CoFe2O4 nanoparticles decorated with Pd JF - Scientific Reports N2 - Decoration with Pd clusters increases the magnetic heating ability of cobalt ferrite (CFO) nanoparticles by a factor of two. The origin of this previous finding is unraveled by element-specific X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) combined with atomic multiplet simulations and density functional theory (DFT) calculations. While the comparison of XAS spectra with atomic multiplet simulations show that the inversion degree is not affected by Pd decoration and, thus, can be excluded as a reason for the improved heating performance, XMCD reveals two interrelated responsible sources: significantly larger Fe and Co magnetic moments verify an increased total magnetization which enhances the magnetic heating ability. This is accompanied by a remarkable change in the field-dependent magnetization particularly for Co ions which exhibit an increased low-field susceptibility and a reduced spin canting behavior in higher magnetic fields. Using DFT calculations, these findings are explained by reduced superexchange between ions on octahedral lattice sites via oxygen in close vicinity of Pd, which reinforces the dominating antiparallel superexchange interaction between ions on octahedral and tetrahedral lattice sites and thus reduces spin canting. The influence of the delocalized nature of Pd 4d electrons on the neighboring ions is discussed and the conclusions are illustrated with spin density isosurfaces of the involved ions. The presented results pave the way to design nanohybrids with tailored electronic structure and magnetic properties. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-14756 SN - 2045-2322 VL - 11 ER -