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Schlagwörter:
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Zusammenfassung:
The ferroelectric and magnetic phases of the double perovskite CaMnTi2O6 with A-site order have been
investigated by soft x-ray absorption and magnetic circular dichroism. All spectra point to a very ionic state of divalent Mn and tetravalent Ti atoms. The effects of the crystal field produced by O ligands around tetravalent titanium and the dissimilar Mn1 and Mn2 sites were investigated. Both the so-called square-planar and the
octahedrally coordinated Mn sites spectroscopically contribute in a rather similar way, with little influence by the oxygen environment. Multiplet calculations suggest a small O 2p-Ti 3d charge-transfer component in the FE phase. Magnetic symmetry calculations were performed to determine probable configurations of Mn spins
compatible with the acentric P42mc structure and, in combination with the computational magnetic results in
Inorg. Chem. 56, 11854 (2017), we have identified the
P4'2m'c as the most likely magnetic space group keeping
invariant the unit cell below TN. This symmetry forces the sign of the magnetic coupling along the Mn columns
parallel to c to reverse with respect to the coupling between neighboring columns. Below TN, the dichroic
magnetization loops at the Mn L3 edge confirm the absence of spontaneous ferromagnetism, although a very
small field-induced spin polarization was detected in the sample.
