December 22, 2023

Enhanced spin current transmissivity in Pt/CoFe2O4 bilayers with thermally induced interfacial magnetic modification

M. Gamino, A. B. Oliveira, D. S. Maior, P. R. T. Ribeiro, F. L. A. Machado, T. J. A. Mori, M. A. Correa, F. Bohn, R. L. Rodríguez-Suárez, J. Fontcuberta, and S. M. Rezende

Phys. Rev. B 2023, 108, 224402;


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 (400C). 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 (θSH) and between the ones of the spin-mixing conductance (geff) in the two samples. We demonstrate that while the value of θSH decreases by one-half with the heat treatment, the value of geff increases by more than one order of magnitude. We interpret the increase of geff 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.

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