Effect of Annealing Conditions in Hydrogen Atmosphere on Structural, Optical and Magnetic Properties of Nanocrystalline CdO Codoped with Cu and Co Ions for DMS Applications

Abstract

Cadmium oxide powder codoped with Cu and Co ions (Cd_0.94Cu_0.01Co_0.05O) was synthesised by thermal co-decomposition of a mixture of cadmium acetate dihydrate, bis(acetylacetonato)copper(II) and bis(acetylacetonato)cobalt(II) complexes. The purpose of the present investigation is to study the effect of H₂-annealing conditions on the evolution of structure, optical and magnetic properties by varying temperature (300, 350 and 400 °C) and duration time (30 and 60 min). X-ray fluorescence (XRF) and X-ray diffraction (XRD) methods confirm the purity and the formation of single nanocrystalline phase of the as-prepared powder; thus, both Cu and Co ions were incorporated into CdO lattice, forming solid solutions. Magnetic measurements reveal that the as-prepared solid solution (SS) gained paramagnetic (PM) properties, although pure CdO itself is considered as diamagnetic (DM). The measured effective magnetic moment of doped Co²⁺ was 3.55 μ _B. Interestingly, it was found that the hydrogenation process could transform the properties of the SS into room-temperature ferromagnetic (RT-FM) only. For example, the coercivity (H _c), remanence (M _r) and saturation magnetisation (M _s) were 279 Oe, 0.187 emu/g and 1.739 emu/g, respectively for SS annealed in H₂ gas at 350 °C for 30 min. Thus, the possibility of producing CdO with RT-FM was proved, where the magnetic characteristics were tailored by doping and post treatment under H₂ gas, thereby a new potential candidate to be used as a dilute magnetic semiconductor (DMS). However, the real effect of H₂ annealing on such drastic transformation in the magnetic behaviour needs some in-depth theoretical research work.