Synthesis, structure, and magnetic behavior of nanoparticles of cubic ZnMnO₃

Role of defects in enhancing room temperature ferromagnetism of Mn doped ZnO nanoparticles

“…It is of the small deviation in respective peak positions is likely to arise due to the local lattice chemical homogeneity and distortions. Thus the obtained nanocrystalline powder sample is abbreviated as the non‐stiochiometric DCS‐ZnMnO 3– δ which is consistent with recently reported ZnMnO 3– δ phase by Rall et al 29 and other researchers 37. In the present synthesis of DCS‐ZnMnO 3– δ phase, above 400 °C calcination temperature, this phase was observed to start dissociating into different phases.…”

“…Cespedes et al 48 named the Mn–Zn–O system as MnO 2– δ /ZnO where MnO 2– δ has distorted environment with high‐density regions of Mn cations. Therefore, in this communication the secondary phase is identified as non‐stoichiometric defect cubic spinel (DCS)‐ZnMnO 3– δ which is consistent with recently reported ZnMnO 3– δ phase by Rall et al 29. Cong et al 30 have observed the major diffraction peaks from the ZnO wurtzite structure along with the similar additional weak peaks of face centered cubic ZnMnO 3 phase at temperatures 750 and 850 °C, however not reported the magnetic nature of secondary phase.…”

“…2b–d). All these obtained minor peaks are not exactly matching with bulk face centered cubic spinel ZnMnO 3 phase (JCPDS No.19–1461) 29–31. The small deviation in respective peak positions is likely to arise due to the local lattice chemical homogeneity and distortions.…”

“…Few people have used notations for assigning such nanocrystalline non‐stiochiometric phase. Rall et al 29 reported non‐stiochicmetric cubic spinel phase as ZnMnO 3– δ and further the structure ZnMnO 3– δ = 3[Zn 2+ ] [Zn 2+ 1/3 Mn 3+ 2/3 Mn 4+ 2/3 □ 1/3 ] O 11/3 with δ = 0.25 of cubic ZnMnO 3 is determined, where □ indicates vacancy at B‐site. Cespedes et al 48 named the Mn–Zn–O system as MnO 2– δ /ZnO where MnO 2– δ has distorted environment with high‐density regions of Mn cations.…”

“…But Jaćimović et al reported superparamagnetism in ZnMnO 3 nanoparticles with blocking temperature of 9 K and no RTFM 36. On the other side recently Rall et al 29 reported ferrimagnetism with T N ≅ 20 K and paramagnetism at 300 K at low field only in defect cubic spinel structured ZnMnO 3 nanoparticles (crystallite size ≅ 25 nm), synthesized by zinc acetate and manganese acetate with the drop wise addition of oxalic acid. According to this reported structure, Mn 3+ and Mn 4+ occupy the B‐sites in equal amounts and ferrimagnetism results from AFM alignment of Mn 3+ and Mn 4+ .…”