Super-exchange interaction model in DMOs: Co doped TiO 2 thin films
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Super-exchange interaction model in DMOs: Co doped TiO2 thin films Heiddy P. Quiroz1,* , E. F. Galı´ndez1, A. Dussan1, A. Cardona-Rodriguez2, and Juan Gabriel Ramirez2 1
Dpto. de Física, Grupo de Materiales Nanoestructurados y sus Aplicaciones, Universidad Nacional de Colombia - Bogotá, Cra. 30 No. 45-03 Edificio 404 Yu Takeuchi Lab. 121C/121B-1 Ciudad Universitaria, Postal Cod. 110001 Bogotá, Colombia 2 Department of Physics, Universidad de los Andes, 111711 Bogotá, Colombia
Received: 6 July 2020
ABSTRACT
Accepted: 1 September 2020
This work presents a study of the structural, morphological, and magnetic properties of TiO2/Co thin films deposited by DC magnetron co-sputtering of Co and TiO2 targets, varying the concentration of the Co and TiO2 at room temperature. The formation of Co oxides binary phases was not observed. From XRD, lXRD, and Raman measurements were identified rutile and anatase phases, which evidence the formation of diluted magnetic oxide semiconductor (DMOs). Additionally, the TiO2 polymorphous and random location of Co ions are induced when the substrate is at room temperature, and in situ annealing process is applied. SEM, AFM, and MFM micrographs evidenced the formation of smaller grains (\ 10 nm) in the surface without relationship with magnetic domains; values of the magnetic roughness were obtained between 199 and 442 pm. Magnetic measurements showed a ferromagnetic-like behavior with the appearance of a magnetic hysteresis loop. The hysteresis curves were associated with a combination of dipolar and super-exchange interactions between Co ions and mediated for oxygen ions based on Anderson’s model; this behavior was described from numerical simulations of isolated magnetic moments (Co atoms) diluted into a non-magnetic matrix (TiO2 structure). In this model, a random distribution of Co ions, contributing to dipolar magnetic interactions and superexchange interaction, is considered, due to the hybridization sp3d2 of the Co–O bond and located randomly of Co ions. The experimental and theoretical results of this study present an explanation of ferromagnetic-like behavior for Co doped TiO2 thin films, as diluted magnetic semiconductor (DMS) for spintronic applications.
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Springer Science+Business
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Handling Editor: Christopher Blanford.
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https://doi.org/10.1007/s10853-020-05282-2
J Mater Sci
GRAPHIC ABSTRACT
Introduction The research and development of the diluted magnetic semiconductors (DMS) have been realized through several fabrication processes and using different semiconductor matrices, such as GaSb/Ni, ZnO/Mn, GaSb/Mn, GaN/Mn, among others [1–4]. In recent years, the study of semiconductor oxides like DMS has evidenced unusual magnetic, electrical, and structural properties associated with the synthesis methods [5] and nanostructure types [6, 7]. Important magnetic properties associated with the oxygen vacancy, structural formation, or changes in the atomic coordination [8, 9] hav
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