Effect of the oxygen deficiency on the physical properties of Ca2MnO4−δ compounds

In this work, structural and magnetic studies have been investigated to explore the influence of the oxygen-deficiency (δ) on the physical properties of Ca₂MnO_4−δ (δ = 0 to 0.5) compounds. The samples cationic stoichiometry has been studied using energy dispersive X-ray analysis (EDAX). EDAX spectra, taken from the surface of the synthesized powders, have showed a nominal composition near the desired one. The structural study, by X-ray diffraction analysis, has confirmed the single-phase composition of all samples. The Rietveld refinement technique of the X-ray patterns, has revealed that samples crystallize in the tetragonal system with I41/acd space group for δ = 0 and in the orthorhombic one with Bbcm space group for δ > 0.The applied magnetic field (μ₀H) and the temperature (T) dependences of the magnetization (M) have been studied using a vibrating sample magnetometer (VSM). From magnetization measurements versus temperature under the field-cooled (FC) and zero-field-cooled (ZFC) modes, we have deduced the presence of a spin-glass behavior characterized by a distinctive separation of the FC and ZFC curves. This behavior was found to become more important, as increasing the oxygen-deficiency δ, which leads to the appearance of magnetic frustration phenomenon.