Crystallisation and Magnetic Properties of Cu/Fe-Codoped Terbium Oxychloride Nanocrystalline Synthesised by Solvothermal Route: Significant Effect of Hydrogenation

Abstract

Terbium oxychloride (TbOCl) nanopowders in pure state and codoped with Cu/Fe dopants were synthesised by a solvothermal route followed by a subsequent heat treatment process. Their structural and optical properties were studied as a function of post-annealing treatment conditions (temperature and atmosphere). The optical properties were studied by the diffuse reflection spectroscopy (DRS) method. Actually, the present work focused on the possible creation of stable room-temperature ferromagnetic (RT-FM) properties within TbOCl. Therefore, dopant impurity iron (Fe2+) ions were used as stable sources of FM properties. However, low doping concentration of Fe2+ could not be able to create FM properties unless followed by annealing in hydrogen-gas atmosphere (hydrogenation). The transition metal (TM) dopant ions (Fe and Cu) could play a role of catalyst in order to dissociate H2 molecules into H atoms during a hydrogenation process. Moreover, dopant Cu ions were also used as donors of polarons to the oxygen vacancies in order to enhance the electronic medium (electromagnetic interference) for spin-spin (SS) long-range interaction. The magnetic measurements reveal that hydrogenated Cu/Fe-codoped TbOCl nanopowders have RT-FM properties with saturation magnetisation of ∼2.2 emu/g. Thus, TbOCl nanocrystals could be used as a potential candidate for optical applications with tailored magnetic properties.