Characterization of europium oxychloride nanopowders codoped with Cu/Ni ions synthesized by solvothermal route: significant effect of post-annealing in hydrogen

Abstract

Europium oxychloride nanopowders codoped with copper/nickel ions were synthesized by solvothermal route followed by a subsequent heat treatment. The present study focuses on determination the conditions required to create stable ferromagnetic (RT-FM) properties in EuOCl crystalline powder. For that purpose, nickel (Ni2+) ions were used as dopant. It was found that such doping could not create FM properties in EuOCl unless followed by hydrogenation. The presence of transition metal (TM) Cu2+ as impurity dopant ions assists to dissociate H2 molecules into H atoms. Moreover, dopant Cu2+ ions donate polarons (electrons) that develop the electronic medium (EMI) of the spin-spin (S.S) long-range interaction in the EuOCl crystalline lattice. Systematic structural, optical, and magnetic properties of pure and Cu/Ni-codoped EuOCl samples were investigated. Their variations with post-annealing treatment in different conditions (temperature and atmosphere) were also studied. The optical properties were studied by diffuse reflection spectroscopy (DRS) method. The magnetic measurements reveal that hydrogenated Cu/Ni-codoped EuOCl nanopowders have RT-FM properties with saturation magnetisation ~ 1.7 emu/g. The physical explanations and discussions were given in the framework of bound magnetic polarons (BMP) theory. Thus, EuOCl nanocrystalline powder could be used as a potential candidate for optical applications with tailored magnetic properties.