Synthesis and magnetic property of spinel Ni_xMn_3-xO₄ nanoparticles by oxidation roasting technology: synergetic reaction and phase evolution behavior

Spinel-type nickel manganate (NiMn₂O₄) has significant application value in areas such as energy storage, sensing, and thermosensitive materials, due to its excellent physical and chemical properties. In this study, during synthesis of Ni_xMn_3-xO₄ (0 < x < 3), the spinel NiMn₂O₄ with a saturation magnetization (Ms) of 3.52 emu/g was synthesized at 1200 °C for 120 min in an air atmosphere with a Ni/Mn molar ratio of 1:2. Additionally, the synthesized NiMn₂O₄ samples had a BET surface area of 3.06 m²/g, a total pore volume of 0.059 cm³/g, a specific surface area (SSA) of 8.87 cm²/g, and an average pore size (APS) of 26.44 nm. Compared with traditional methods, the simultaneous presence of normal and inverse spinel NiMn₂O₄ was prepared by oxidation roasting technology, resulting in slight differences in crystal structure parameters. This work demonstrates that the oxidation roasting process is an effective route for synthesizing spinel nickel manganate (NiMn₂O₄), where normal and inverse spinel structures inevitably coexist and intertransform, with their ratio being controlled by synthesis parameters.