Browsing by Author "Correa, M. A."

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Enhanced spin current transmissivity in Pt/CoFe2O4 bilayers with thermally induced interfacial magnetic modification
    (2023) Gamino, M.; Oliveira, A. B.; Maior, D. S.; Ribeiro, P. R. T.; Machado, F. L. A.; Mori, T. J. A.; Correa, M. A.; Bohn, F.; Rodriguez-Suarez, R. L.; Fontcuberta, J.; Rezende, S. M.
    We report on processes of generation of spin current and conversion into charge current in CoFe2O4/Pt bilayers by means of spin Hall magnetoresistance (SMR) and spin Seebeck effect (SSE) experiments. Specifically, we explore (001) full-textured CoFe2O4 (CFO) thin films grown onto (001)-oriented SrTiO3 substrates, covered with Pt layers deposited under two different conditions: one at room temperature and another at high temperature (400 degrees C). The x-ray absorption spectroscopy measurements indicate that the Pt layer deposited at high temperature induces an interfacial magneticlike phase (Fe,Co)-Pt alloy, which influences the magnetic behavior of the structure and is responsible for the enhancement of the spin transmission at the interface. By analyzing the SMR data, we conclude that collinear and noncollinear magnetic domains coexist at the CFO-(Fe,Co)-Pt interface. By combining the data from the SMR and SSE measurements, we obtain the ratios between the values of the spin Hall angle (theta SH) and between the ones of the spin-mixing conductance (g up arrow down arrow that while the value of theta SH decreases by one-half with the heat treatment, the value of g up arrow down arrow one order of magnitude. We interpret the increase of g up arrow down arrow eff in terms of unexpected magnetic reconstructions, which produce an enhancement of the magnetic moment arisen at the interface. Since the spin-mixing conductance determines the efficiency of the spin current transmission through the interface, the spinel ferrite cobalt in contact with a normal metal with a suitable heat treatment becomes a promising material for spintronics device applications.
  • Thumbnail Image
    Item
    Filtering magnetic relaxation mechanisms of YIG(001) thin films using ferromagnetic resonance
    (ELSEVIER, 2020) Oliveira, A. B.; Rodriguez Suarez, R. L.; Correa, M. A.; Bohn, F.; Raza, S. A.; Sommer, R. L.; Chesman, C.
    In this work we used the ferromagnetic resonance (FMR) technique to measure the contributions for the magnetic relaxation in Y3Fe5O12 textured films deposited onto (001) Gd3Ga5O12 by magnetron sputtering. Through the numerical fitting of the angular dependence of the in-plane FMR linewidth measurements we identified the contribution of the Gilbert, two-magnon and mosaicity relaxation mechanisms. Regarding to the line broadening due to two-magnon mechanism, we interpreted it as a result of rectangular defects distributed over the film plane. The overall defects were decomposed into three crystallography direction chosen according to the in-plane FMR resonance field experimental results. We observed the two-magnon scattering rate being relevant for YIG thickness below 150 nm. Although it is also present for thicker samples, the Gilbert mechanism dominates with mosaicity being very important to corroborate the shape of the angular dependence, but with small amplitude. We point out the relevance of our finding regarding two-magnon scattering effect in YIG thin films, directly impacting in an overestimation of the spin pumping contribution to the FMR line broadening in YIG/ heavy-metal systems.
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    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.