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Mn Self-Doping of Orthorhombic RMnO<sub>3</sub> Perovskites: (R<sub>0.667</sub>Mn<sub>0.333</sub>)MnO<sub>3</sub> with R = Er–Lu
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Citations
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References
2018
Year
Orthorhombic rare-earth trivalent manganites RMnO<sub>3</sub> (R = Er-Lu) were self-doped with Mn to form (R<sub>0.667</sub>Mn<sub>0.333</sub>)MnO<sub>3</sub> compositions, which were synthesized by a high-pressure, high-temperature method at 6 GPa and about 1670 K from R<sub>2</sub>O<sub>3</sub> and Mn<sub>2</sub>O<sub>3</sub>. The average oxidation state of Mn is 3+ in (R<sub>0.667</sub>Mn<sub>0.333</sub>)MnO<sub>3</sub>. However, Mn enters the A site in the oxidation state of 2+, creating the average oxidation state of 3.333+ at the B site. The presence of Mn<sup>2+</sup> was confirmed by hard X-ray photoelectron spectroscopy measurements. Crystal structures were studied by synchrotron powder X-ray diffraction. (R<sub>0.667</sub>Mn<sub>0.333</sub>)MnO<sub>3</sub> crystallizes in space group Pnma with a = 5.50348(2) Å, b = 7.37564(1) Å, and c = 5.18686(1) Å for (Lu<sub>0.667</sub>Mn<sub>0.333</sub>)MnO<sub>3</sub> at 293 K, and they are isostructural with the parent RMnO<sub>3</sub> manganites. Compared with RMnO<sub>3</sub>, (R<sub>0.667</sub>Mn<sub>0.333</sub>)MnO<sub>3</sub> exhibits enhanced Néel temperatures of about T<sub>N1</sub> = 106-110 K and ferrimagnetic or canted antiferromagnetic properties. Compounds with R = Er and Tm show additional magnetic transitions at about T<sub>N2</sub> = 9-16 K. (Tm<sub>0.667</sub>Mn<sub>0.333</sub>)MnO<sub>3</sub> exhibits a magnetization reversal or negative magnetization effect with a compensation temperature of about 16 K.
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