We present a study of the properties related to the magnetization reversal process in two thin-film samples with magnetic stripe domains: Fe0.82Ga0.18 (Fe-Ga) and Ni0.81Fe0.19 (permalloy). In Fe-Ga thin films, we focus on magnetization reversal driven by thermal activation by considering the magnetic viscosity behavior. The results suggest that the reversal process occurs gradually, where the magnetization switches direction via similar to 10 nm-long jumps of the magnetic domain walls. On the other hand, vectorial hysteresis loops were performed in permalloy thin films with the aim to study the behavior of the transverse magnetization component (perpendicular to the applied field) during the magnetization reversal process. We show that the measurement of the transversal magnetization component shows a much higher sensitivity for the determination of the in-plane magnetic anisotropy than the usual hysteresis loops where the magnetization is parallel to the applied field. Moreover, this allows to highlight the competition between the intrinsic and rotatable anisotropies in thin films that present stripe domains.

Received 13 March 2024DOI:https://doi.org/10.1103/PhysRevB.109.099901©2024 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMagnetic textureMagnetostrictionPhysical SystemsThin filmsTechniquesMagnetization measurementsX-ray diffractionCondensed Matter, Materials & Applied Physics

In this study, we present a systematic analysis of the relation between the structural properties and magnetic anisotropies of as-grown and heat-treated polycrystalline Fe (1 - x) Ga (x) (0.11 < x < 0.19) thin films deposited on glass and Si(100) substrates. The results show that the crystallographic texture of the films has a significant impact on the evolution of the magnetic anisotropies. The samples grown on glass do not exhibit a preferred texture while, for samples grown on Si(100), the appearance of a weak in-plane fourfold magnetic anisotropy is reported. Such anisotropy is enhanced and better defined in the heat treated samples. Via a phenomenological model we show that this anisotropy has a microstructural origin. These findings demonstrate the possibility of tuning magnetic anisotropies by growing on different substrates and/or performing thermal treatments, which in turn reinforces the possibility of developing smart magnetic switching materials for electronic applications.

In this work, we have investigated the coexistence of volatile and nonvolatile memristive effects in epitaxial phase-separated La0.5Ca0.5MnO3 thin films. At low temperatures (50 K), we observed volatile resistive changes arising from self-heating effects in the vicinity of a metal-to-insulator transition. At higher temperatures (140 and 200 K), we measured a combination of volatile and nonvolatile effects arising from the synergy between self-heating effects and ferromagnetic-metallic phase growth induced by an external electrical field. The results reported here add phase separated manganites to the list of materials that can electrically mimic, on the same device, the behavior of both neurons and synapses, a feature that might be useful for the development of neuromorphic computing hardware.

In this work, we study the magnetoelastic behavior of Fe1-xGax (0.11 < x < 0.19) thin films, grown on glass and oxidized Si(100) amorphous substrates, that present an isotropic crystalline texture in the film plane. The magnetoelastic coupling coefficients are obtained through the cantilever deflection technique. We find that the magnetoelastic response is larger for samples grown on glass with respect to those grown on Si(100), and such a response increases for larger Ga concentrations for both substrates used. Furthermore, the increasing substrate temperature during growth does not appear to have a significant effect on magnetoelastic behavior of samples grown on Si(100). From a model that takes into account the elastic grain interaction for isotropic systems, we are able to describe the experimentally observed behavior. We find that the magnetoelastic response of the samples grown on glass are well described by the Voigt model, while the samples on Si(100) present an intermediate response between the Voigt and Reuss models.

In this work we have investigated the influence of Ar sputtering pressure (PAr) in the magnetic properties of polycrystalline sputtered Fe0.89Ga0.11 thin films. The structural characterization shows that the samples are composed by several fiber-like crystallographic textures in which the fiber axis is always along the growth direction, whereas their portion weights evolve with PAr during the sputtering deposition. Magnetometry and ferromagnetic resonance (FMR) experiments evidence the existence of a perpendicular magnetic anisotropy (PMA) that increases systematically for increasing PAr. By proposing a model that takes into account the interfacial, magnetoelastic and magnetocrystalline contributions to the magnetic free energy, we find that the magnetocrystalline one appears as the main responsible of the increasing PMA. The PMA values estimated from the model predict satisfactorily the experimental values obtained from FMR.

In this work, we present a systematic study on the relation between the elastic behavior and the structural properties of polycrystalline Fe0.89Ga0.11 thin films deposited on Si(100) substrates. By carrying out pole figure (PF) measurements, we determined the evolution of the texture components, residual stress and Young's modulus (Ys) as a function of the Ar pressure. The samples display several fiber-like texture components (where the fiber axes is always along the growth direction) beside to a random component; the texture component weights depend on the Ar pressure. The study of the residual stress reveals that the samples present a tensile stress, that relaxes when the Ar pressure increases. In the case of Ys, the estimated values vary slightly within the Ar pressure range studied. Finally, the residual stress and Ys behavior is correlated with the microstructure evolution by using the orientation distribution function (ODF) simulated from the PFs.

In this work we present a careful study on the relationship between the magnetic and structural properties of a highly magnetostrictive Fe0.89Ga0.11 (Fe-Ga) alloy deposited onto glass, Si and MgO substrates. When grown on glass, the films are polycrystalline with randomly oriented grains without any texture, while the ones on Si and MgO present preferred growth directions. Fe-Ga/Si films show a [1 1 3] fibre-like texture, and Fe-Ga/MgO presents a quasi monocrystalline behavior with the (1 0 0) film plane direction parallel to the substrate surface. When Fe-Ga/MgO films are annealed an additional (1 1 0) texture is also observed. Magnetometry and ferromagnetic resonance (FMR) show that the magnetic behavior is closely related to the structural observed textures. Furthermore, the structural analysis allowed us to get a deeper understanding of the magnetic behavior. This point is very important to get the ability of controlling the crystalline texture by means of growing onto different substrates and/or thermal treatments, which in turns opens the possibility of handling the magnetic texture which is particularly important in magnetostrictive materials for electronic devices.

A general thermodynamic consistency test is applied to analyze phase equilibrium data (TPxy data) for binary water + congener mixtures found in alcoholic distillation processes. The congeners, substances that are present at very low concentration in a must, considered in this study are: acetic acid, acetaldehyde, ethyl acetate, furfural, methanol, 1-propanol, methyl acetate and 2-butanol. The thermodynamic test combines the Peng-Robinson equation of state modified by Kwak and Mansoori for correlating phase equilibrium data and the Gibbs-Duhem equation to check for consistency. The test is applied to analyze twenty five isothermal P-x-y data of water+congener mixtures obtained from the literature. Of the 25 sets of data, 18 are found to be thermodynamically inconsistent. In several cases, the results are in agreement with information from the literature in which these same systems are considered to be thermodynamically inconsistent using a test that uses activity coefficients for the liquid phase. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.