Influence of Co and Co-F co-doping on defect-induced intrinsic ferromagnetic properties of PbPdO2 nanoparticles

Abstract

In this work, Co-doped and Co-F co-doped PbPdO2 nanoparticles with a body-centered orthorhombic structure were synthesized via sol–gel method. The measured results reveal that, Pb and O vacancies exist in all samples; the valence state of magnetic atom Co is identified as mixed Co2+ and Co3+; all samples exhibit both ferromagnetism and paramagnetism; the incorporation of fluorine results in an evident increase in the magnetic moment of PbPd0.875Co0.125O2@F; a jump of magnetization at about 265 K can be found in both FC and ZFC curves of PbPd1-xCoxO2 (x = 0, 0.05, 0.10 and 0.115). Moreover, the origin of the magnetism can be considered as follows: the ferromagnetism for PbPd1-xCoxO2 (0 < x ≤ 0.15) results from the combined effect of O1− and magnetic Co ions; fluorine substitution in an oxygen lattice site and the fluorine doping in the interstitial sites can induce both distinct roles on the valence of oxygen, Co and Pd ions, which changes evidently the magnetic properties of PbPd1-xCoxO2. Fortunately, the magnetic properties of PbPdO2, Co-doped PbPdO2, Co-F co-doped PbPdO2 can be verified by first-principles calculations. It is found that the enhanced magnetization results mainly from Pd(2−δ)+ and more O1− induced by F. Finally, the magnetization jump at about 265 K has been explained by the temperature-dependent valence transformation between O2− and O1−.