Room temperature ferromagnetic phase in ZnO–MnO2 system via solid-state reaction

Abstract Only mechanical milling of a mixture of powders composed of MnO2 and ZnO brings about a phase which exhibits ferromagnetic behavior at room temperature. The sample just after the mechanical milling without any heat treatments at elevated temperatures clearly manifests a hysteresis loop in magnetic field dependence of magnetization at 300 K; the residual magnetization is 2.84×10−4 emu/g and the coercive force is 76 Oe. It should be emphasized that the residual magnetization rather decreases when the as-milled sample is heat treated. The ferromagnetic behavior is thought to be attributed to Zn-doped manganese oxide phase formed on the surface region of MnO2 particles.