Browsing by Author "Rodriguez-Suarez, R. L."

Now showing 1 - 6 of 6
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    Analytical solutions for the magnon frequencies at high-symmetry points of the Brillouin zone in anisotropic kagome antiferromagnets
    (2021) Rodriguez-Suarez, R. L.; Rezende, S. M.
    The knowledge of the magnon dispersion relations in antiferromagnetic materials with nontrivial spin textures has considerable interest to the understanding of magnonic and spintronic phenomena involving these materials. One particularly interesting nontrivial spin texture existing in several antiferromagnets has spins at an angle of 120 degrees with the in-plane neighbors and arranged in kagome lattices. Here we present a spin-wave calculation for antiferromagnets with kagome spin lattices considering exchange and single-ion anisotropy interactions between the spins. The theory yields exact analytical expressions for the frequencies of magnons at high-symmetry points of the Brillouin zone, that can be readily use to obtain the interaction parameters from experimental data with one-and two-magnon inelastic light scattering. The analytical expressions are used to obtain the field parameters for the kagome lattice antiferromagnet L1(2)-IrMn3 from four experimentally measured frequencies. Both exchange field parameters are in reasonable agreement with the values obtained with ab initio calculations, while the anisotropy field is in very good agreement with the one calculated with atomistic spin models and Monte Carlo simulations.
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    Exploring orbital-charge conversion mediated by interfaces with CuOx through spin-orbital pumping
    (2024) Santos, E.; Abrao, J. E.; Vieira, A. S.; Mendes, J. B. S.; Rodriguez-Suarez, R. L.; Azevedo, A.
    We explore the impact of different materials on orbital-charge conversion in heterostructures with a naturally oxidized copper capping layer. Introducing a thin layer of CuOx (3 nm) to the yttrium iron garnet (YIG)/W heterostructure resulted in a notable decrease in signal when employing the spin pumping (SP) technique. This contrasts with prior findings in YIG/Pt, where the addition of CuOx (3 nm) led to a significant signal enhancement. Conversely, the introduction of the same CuOx (3 nm) layer to YIG/Ti (4 nm) structure showed no change in the SP signal. This lack of change is attributed to the fact that Ti, unlike Pt, does not generate an orbital current at the Ti/CuOx interface due to its weaker spin-orbit coupling. Notably, incorporating the CuOx (3 nm) layer on top of Si/Py (5 nm)/Pt (4 nm) structures resulted in a substantial increase in the spin pumping signal. However, in Si/CuOx (3 nm)/Pt (4 nm)/Py (5 nm) structures, the signal exhibited a decrease. Finally, we applied a phenomenological model of the spin (orbital) Hall effect in YIG/heavy-metal systems to refine our data. These discoveries have the potential to advance research in the innovative field of orbitronics and contribute to the development of new technologies based on spin-orbital conversion.
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    Longitudinal spin Seebeck effect and anomalous Nernst effect in CoFeB/non-magnetic metal bilayers
    (2021) Gamino, M.; Santos, J. G. S.; Souza, A. L. R.; Melo, A. S.; Della Pace, R. D.; Silva, E. F.; Oliveira, A. B.; Rodriguez-Suarez, R. L.; Bohn, F.; Correa, M. A.
    We investigate the longitudinal spin Seebeck effect in CoFeB/NM bilayers, with Ta, Pd and Ru as non-magnetic NM material. By means of a quantitative approach using an equivalent circuit model, we determine the accurate voltage due inverse spin Hall effect measured in the non-magnetic layer beyond unveiling the role of anomalous Nernst effect and thermoeletric effects provide by metallic ferromagnetic CoFeB layer. From experimental results, we estimate the spin Seebeck coefficient for the bilayers, finding values quite compatible with those for ferromagnetic insulators reported in literature. Moreover, we address the angular dependence of the voltage curves, disclosing the non-magnetic layer affects the effective magnetic anisotropy of the whole bilayer. Hence, our results suggest the effective magnetic anisotropy may be modified to improve the thermoelectric voltage response in ferromagnetic/non-magnetic metal bilayers.
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    Spin pumping contribution to the magnetization damping in Tm3Fe5O12/W bilayers
    (2022) Oliveira, A. B.; Rodriguez-Suarez, R. L.; Vilela-Leao, L. H.; Vilela, G. L. S.; Gamino, M.; Silva, E. F.; Bohn, F.; Correa, M. A.; Moodera, J. S.; Chesman, C.
    In this work, thulium iron garnet (Tm3Fe5O12 - TmIG (20 nm)/Tungsten(W)(t) bilayers, sputtered on top of gadolinium gallium garnet (111) substrate, were used to investigate spin pumping (SP) line broadening mechanism in Ferromagnetic Resonance (FMR). The TmIG, films prior and after tungsten cap layer deposition, were investigated employing FMR and X-ray diffraction techniques. The TmIG films showed (1 1 1) orientation and perpendicular magnetic anisotropy (PMA). Due to the interface TmIG/W, when the TmIG magnetization is in resonance a spin current is pumped out the TmIG into the W layer, increasing the damping of the magnetization. Measuring the out-of-plane angular dependence of the FMR resonance field and linewidth, we were able to obtain solely the SP contribution to the line broadening, filtering Gilbert, mosaicity, and two magnon scattering mechanisms.
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    The role of metallic nanoparticles in the enhancement of the spin Hall magnetoresistance in YIG/Pt thin films
    (2018) Gamino, M.; Silva, E. F.; Alves Santos, O.; Mendes, J. B. S.; Rodriguez-Suarez, R. L.; Machado, F. L. A.; Azevedo, A.; Rezende, S. M.
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    Theory for the spin caloritronic nano-oscillator
    (2022) Rezende, S. M.; Rodriguez-Suarez, R. L.
    Auto-oscillations of the magnetization in ferromagnetic hybrid nanostructures driven by spin currents produced by a variety of processes have attracted attention for their challenging physics and possible applications, such as microwave assisted magnetic recording, neuromorphic computing, and chip to chip wireless communications. Of particular interest are applications in which the spin current is produced by a thermal gradient in the configuration of the spin Seebeck effect, because it makes it possible to harvest the thermal energy generated in nanodevices. A few years ago, it was demonstrated experimentally that in a simple bilayer made of a thin film of the insulating ferrimagnet yttrium iron garnet in contact with a platinum layer, the application of a temperature difference across the bilayer produced a coherent microwave auto-oscillation. This device was called a spin caloritronic nano-oscillator. Here we show that these experiments are explained quantitatively by a theory based on a mechanism in which one magnon in the spin current splits into two magnons, one of them being the magnon mode resonating at the nanostructure. The theoretical value of the critical temperature gradient necessary to overcome the magnetic damping to produce auto-oscillations is in good agreement with the one employed in the experiments.