Negative magnetization, shielding current effect and divalent manganese in CaMn1-xTaxO3 manganites

• Published in: Journal of alloys and compounds 2023-12, Vol.967, Article 171686
• Main Authors: Ulyanov, A.N., Yang, Dong-Seok, Savilov, S.V.
• Format: Article
• Language: English
• Subjects: Crystal structure; Electron doped manganites; Electronic structure; Negative magnetization; XANES
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2023.171686

Crystal and electronic structures, and magnetic properties of polycrystalline tantalum substituted manganites CaMn1-xTaxO3 (x = 0.00, 0.03, 0.06, 0.09 and 0.12) were studied by x-ray diffraction, x-ray absorption near edge spectroscopy (XANES) at Mn K-edge, and by magnetization measurements. Large changes of cell volume and magnetic transition temperature, in addition to shift of Mn K-edge spectra and change of shape of XANES spectra, indicate the existence of Mn3+ as well as Mn2+ species induced by the substitution of Mn4+ by Ta5+. Cell parameters and cell volume increase with increasing x because the Mn3+, Mn2+ and Ta5+ ions are larger that substituted Mn4+ ion. According to XANES results, at least the x = 0.00 sample is oxygen deficient. The negative magnetization was observed in the CaMnO3-δ sample, and a possible explanation of the phenomenon is given considering two canted (almost antiferro)magnetic sublattices and a shielding current, associated with the itinerant eg electrons, induced by the oxygen vacancies. •Negative magnetization (NM) and divalent manganese are observed in CaMn1−xTaxO3-δ.•NM caused by canted antiferromagnetic (AFM) states and eg electron shielding current.•AFM state and shielding current originate from Ta- and/or oxygen vacancy- content.•Large decrease in TC and change in shape of XANES spectra due to Mn2+ are observed.