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Sol-gel based synthesis and magnetic, dielectric and optical properties study of nanocrystalline Sr3Co2WO9 triple perovskite

Perovskite materials have attracted extensive attention due to their fascinating properties and novel features attributed to the coexistence of ferro/ferri/antiferro-magnetic ground state and semiconductor band gap within the same material. In this research, triple perovskite Sr3Co2WO9 has been successfully synthesized for the first time in the nanocrystalline form with an average crystallite size of 23 nm by means of a modified aqueous citrate sol-gel method. At room temperature, the crystal structure of Sr3Co2WO9 is cubic, space group Fm-3m with lattice parameter a = 7.9073(6) Å. The formation of Sr3Co2WO9 was studied in situ by X-ray diffraction and analysed by the Rietveld analysis. The detected hysteresis loops with non-zero remanent magnetization and rather large coercive field reveal ferrimagnetic ordering with Curie temperature of 144 K. The measured effective magnetic moment of 3B is close to the expected value for rarely observed intermediate spin S = 1. However, this can be also explained as a combination of LS (60 %) and HS (40 %) Co3+. It is found that the compound exhibits the semiconducting properties with the optical band gaps equal to 3.52 eV (indirect) and 3.76 eV (direct), respectively. This was confirmed by AC conductivity measurements, which varies between 10−5 and 10−4 Ω−1 cm−1. The Maxwell -Wagner model is employed to describe the frequency dependent dielectric constant. The frequency dependent AC conductivity follows the universal Jonscher’s power law. Semiconducting properties of this materials could thus be spincontrolled if implemented in devices.

triple perovskite ; cobalt ; tungsten ; ferrimagnetic ; semiconductor

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