Synthesis, Characterization, and DFT Investigation of the Role of Oxygen Vacancy on the Structural, Magnetic, and Electronic Properties of La2CoMnO6

• Published in: Journal of superconductivity and novel magnetism Vol. 35; no. 6; pp. 1405 - 1412
• Main Authors: Harbi, A., Azouaoui, A., Benmokhtar, S., Moutaabbid, M.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.06.2022
• Subjects: Characterization and Evaluation of Materials; Condensed Matter Physics; Magnetic Materials; Magnetism; Physics; Physics and Astronomy; Review; Strongly Correlated Systems; Superconductivity; Super-exchange interaction; Perovskite double; Ferromagnetism; Half metallicity; Oxygen vacancy
• ISSN: 1557-1939; 1557-1947
• DOI: 10.1007/s10948-022-06239-z

La 2 CoMnO 6 double perovskite was synthesized by the solid-state reaction method, and its crystal structure was investigated using X-ray diffraction and Raman spectroscopy. The crystal structure of the study compound has been verified to possess monoclinic crystal symmetry, space group P2 1 /n with the lattice parameters a  = 5.53 Å, b  = 5.48 Å, c  = 7.77 Å, and β  = 89.9°. The Raman spectrum shows two broad peaks, the high-frequency peak near 668 cm −1 corresponding to the A g stretching mode, whereas the low-frequency peak near 522 cm −1 corresponding to the B g anti-stretching and bending modes. The electronic and magnetic properties of pure and defective perovskite La 2 CoMnO 6 have been carried out using the density functional theory (DFT). The result shows a ferromagnetic insulator character for pure perovskite; the ferromagnetic state is explained by super-exchange interaction between empty and half-filled e g orbitals of Mn 4+ ( t 2 g 3 e g 0 ) and Co 2+ ( t 2 g 5 e g 2 ) via oxygen O 2− . The valence band maximum (VBM) begins primarily from the p-states of oxygen atom and d-states of transition metal (Mn and Co), while the conduction band minimum (CBM) comprises both d-states of the M-site transition metal and f-state of lanthanum. The creation of oxygen defect leads to the lattice expansion due to a Coulomb repulsion between the Co atom and Mn atom as oxygen is no longer their nearest neighbor (NN). The oxygen vacancy also reveals a half metallicity character with a bandgap in the spin-up channel and a continuous band at the Fermi level in the spin-down channel. The calculated Curie temperature T C decreased (pure T c  = 422 K and defective T c  = 378 K) as decreasing the bond angle Mn- O ^ 3 -Co (pure Mn- O ^ 3 -Co = 150.13° and defective Mn- O ^ 3 -Co = 146.026°).