Investigation of structural and magnetic properties of Mg0.946Cu2.054O3 compound

•Antisite defects are present, with some Cu atoms substituting Mg atomic sites.•A broad peak in the susceptibility curve indicates disorder in the system.•Short-range order and antisite defects contribute to the disorder.•Low-temperature heat capacity measurements confirm the presence of short-range order.•Fitting of specific heat data using Debye + Einstein model. The crystal structure of synthesized Mg0.946Cu2.054O3 compound was examined using Rietveld refinement of powder X-ray diffraction (XRD), revealing the presence of antisite defects in the form of substitution occupation of Mg atomic sites by Cu atoms upto ∼9 %. Detailed investigation by magnetic measurements around antiferromagnetic Néel transition around 95 K and below hints at the existence of paramagnetic component and short-range order due to presence of antisite defects, which is further supported by specific heat measurements.