<i>A</i>‑Site-Doping
Enhanced <i>B</i>‑Site Ordering and Correlated Magnetic
Property
in La<sub>2–<i>x</i></sub>Bi<sub><i>x</i></sub>CoMnO<sub>6</sub>
- Publication date
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Abstract
A series of Bi-doped La<sub>2–<i>x</i></sub>Bi<sub><i>x</i></sub>CoMnO<sub>6</sub> 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 <i>B</i>-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<sub>2</sub>CoMnO<sub>6</sub>, LaBiCoMnO<sub>6</sub>, and Bi<sub>2</sub>CoMnO<sub>6</sub>. Moreover, we find a
spin-state transition in the antisite Co ions from high-spin (Co<sup>2+</sup>-t<sub>2g</sub><sup>5</sup>e<sub>g</sub><sup>2</sup>) to
low-spin state (Co<sup>3+</sup>-t<sub>2g</sub><sup>6</sup>e<sub>g</sub><sup>0</sup>), which is consistent with the increased total magnetic
moments by the Bi doping