A series of Bi-doped La 2-xBi xCoMnO 6 double perovskite oxides are synthesized, and the impact of doping on crystal structures and magnetic properties is investigated comprehensively. X-ray photoelectron spectroscopy and Raman spectrum analyses reveal that ordering of Co and Mn ions at B-site is gradually improved with the rise of Bi concentration. Meanwhile, magnetic disordering is suppressed greatly by showing larger magnetic moments. Structurally, the Rietveld refinement shows that the bonds are elongated, while the bond angles are shrunken after doping, giving rise to lowered Curie temperature. We also observe a large negative zero-field-cooling magnetization, which is attributed to the formation of spin antiparallel or canted ferromagnetic domains and clusters that are separated by the antiphase boundaries. First-principles calculations confirm the enhanced Co-Mn ordering upon Bi doping by taking into account both the ordering and disordering configurations of La 2CoMnO 6, LaBiCoMnO 6, and Bi 2CoMnO 6. Moreover, we find a spin-state transition in the antisite Co ions from high-spin (Co 2+-t 2g 5e g 2) to low-spin state (Co 3+-t 2g 6e g 0), which is consistent with the increased total magnetic moments by the Bi doping.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Electronic, Optical and Magnetic Materials
- Surfaces, Coatings and Films