Structural and magnetic properties of nanocrystalline equi-atomic spinel high-entropy oxide (AlCoFeMnNi)3O4 synthesised by microwave assisted co-precipitation technique

• Microwave assisted synthesis process could provide high-entropy oxide (HEO). • Monophasic sample displayed cubic spinel structure. • It was ferrimagnetic at RT and a transition temperature of 538 K during field warming. • The chemical disorder nature of the material effectively modifies the magnetic behaviour. Single phase equi-atomic (Al 0.2 Co 0.2 Fe 0.2 Mn 0.2 Ni 0.2 ) 3 O 4 high-entropy oxide (HEO) having spinel structure was synthesised employing simple and cost effective microwave assisted co-precipitation technique, followed by calcination at 500 °C. The material obtained was highly crystalline and stable at higher temperatures. The uniformity in elemental distribution was apprehended through STEM-EDS elemental mapping. The X-ray photoelectron spectroscopy confirmed +3 ionic state for Fe and Al, while other elements oxidised to higher ionic states to maintain charge neutrality. Ferrimagnetic behaviour was confirmed for the obtained HEO through magnetic characterisations.