Magnetic nanopatterns were successfully created in FeRh thin film deposited on MgO (100) substrates. Silica and polystyrene spherical masks, nominally 500 and 1000 nm in diameter, respectively were applied on the surface of the sample in order to locally shadow the film against the effect of 110 keV energy neon-ion irradiation with fluences of 10¹⁵ and 10¹⁶ ions/cm². Such nanosphere-lithography technique allows for projecting the mask geometry on the magnetic structure of the FeRh film. Conversion-electron Mössbauer spectroscopy and magnetic force microscopy were used to determine the ferromagnetic ratio and the magnetic pattern in the samples, and nuclear resonance scattering of synchrotron radiation was applied to obtain the in-depth magnetic profile. From the results obtained, the possible three-dimensional (3D) structure of the created individual magnetic domains was also constructed. Overall, the great customizability of the presented nanosphere-lithography technique in FeRh thin film provides opportunities for developing cutting-edge spintronic applications.

Reducing the material sizes to the nanometer length scale leads to drastic modifications of the propagating lattice excitations (phonons) and their interactions with electrons and magnons. In EuO, a promising material for spintronic applications in which a giant spin-phonon interaction is present, this might imply a reduction of the degree of spin polarization in thin films. Therefore, a comprehensive investigation of the lattice dynamics and spin-phonon interaction in EuO films is necessary for practical applications. We report a systematic lattice dynamics study of ultrathin EuO(001) films using nuclear inelastic scattering on the Mössbauer-active isotope ¹⁵¹Eu and first-principles theory. The films were epitaxially grown on YAlO₃(110), which induces a tensile strain of ca. 2%. By reducing the EuO layer thickness from 8 nm to a sub-monolayer coverage, the Eu-partial phonon density of states (PDOS) reveals a gradual enhancement of the number of low-energy phonon states and simultaneous broadening and suppression of the peaks. These deviations from bulk features lead to significant anomalies in the vibrational thermodynamic and elastic properties calculated from the PDOS. The experimental results, supported by first-principles theory, unveil a reduction of the strength of the spin-phonon interaction in the tensile-strained EuO by a factor of four compared to a strain-free lattice.

Iron-germanides are widely investigated due to their possible application in nanoelectronics and spintronics applications. The feasibility of these materials in industrial application is highly dependent on their structural stability against temperature, therefore it is indispensable to understand temperature induced diffusion processes in this system. In order to study iron self-diffusion, [57Fe5Ge3(36 Å)/nFe5Ge3(62 Å)]10 isotope-periodic multilayer was prepared by molecular beam epitaxy. By using neutron reflectivity technique, which is sensitive to atomic scale diffusion lengths, we have determined the pre-exponent factor and activation energy as D0 = (8.22 ± 3.8) × 10-18 m2s−1 and Ea = (0.28 ± 0.02) eV respectively.

The effect of laser irradiation in the energy range from 20 mW to 200 mW was investigated in 109 nm thick Fe₅₁Rh₄₉ film deposited on an MgO (100) substrate. The initial, A1 structure with fully paramagnetic magnetic ordering was achieved after irradiating the samples with 120 keV Ne⁺ ions with a fluence of 1 × 10¹⁶ ion cm⁻², as it was confirmed by conversion-electron Mössbauer spectroscopy. At higher powers physical damage of the layer was observed, while in the lowest power case, magnetic force microscopy revealed a well-defined magnetic structure reflecting the laser irradiation pattern. The presented results have the potential to be employed for laser ablation or allows the fabrication of arbitrary ferromagnetic pattern within a homogeneous paramagnetic FeRh thin films.

To design custom magnetic nanostructures, it is indispensable to acquire precise knowledge about the systems in the nanoscale range where the magnetism forms. In this paper we present the effect of a curved surface on the evolution of magnetism in ultrathin iron films. Nominally 70 Å thick iron films were deposited in 9 steps on 3 different types of templates: (a) a monolayer of silica spheres with 25 nm diameter, (b) a monolayer of silica spheres with 400 nm diameter and (c) for comparison a flat silicon substrate. In situ iron evaporation took place in an ultrahigh vacuum chamber using the molecular beam epitaxy technique. After the evaporation steps, time differential nuclear forward scattering spectra, grazing incidence small angle X-ray scattering images and X-ray reflectivity curves were recorded. In order to reconstruct and visualize the magnetic moment configuration in the iron cap formed on top of the silica spheres, micromagnetic simulations were performed for all iron thicknesses. We found a great influence of the template topography on the onset of magnetism and on the developed magnetic nanostructure. We observed an individual magnetic behaviour for the 400 nm spheres which was modelled by vortex formation and a collective magnetic structure for the 25 nm spheres where magnetic domains spread over several particles. Depth selective nuclear forward scattering measurements showed that the formation of magnetism begins at the top region of the 400 nm spheres in contrast to the 25 nm particles where the magnetism first appears in the region where the spheres are in contact with each other.

Both preserved gapless states and gapping of Dirac states due to broken time reversal symmetry in bismuth chalcogenide topological insulators with surface and bulk magnetic impurities have been observed and reported in the literature. In order to shed more light on the mechanism of such effects we have performed comprehensive element selective study of the impact of Fe impurity position in the Bi₂Se₃ lattice on its magnetism. The iron atoms were imbedded in the structure (volume dopants) or deposited on the surface (adatoms) and they revealed striking phenomena. Volume doping preserves non-trivial topology of Bi_1.98Fe_0.02Se₃. Fe atoms not only substitute Bi, but also locate in van der Waals gap. The former are magnetically isotropic, while the latter reveal large magnetic moment (4.5 μ _B) with perpendicular anisotropy if located near the surface. Majority of Fe adatoms on the surface of Bi₂Se₃ exhibit weaker moment (3.5 μ _B) with in-plane anisotropy, as expected for non-interacting species. Negligible interaction between surface electronic states and magnetic adatoms is confirmed by identical vibration spectra of Fe deposited on TI surface of Bi₂Se₃ and non-TI surface of Bi₂S₃. The data gathered show how indispensable is the knowledge of the magnetic impurity distribution for applications of bismuth chalcogenide systems.