Mn Self-Doping of Orthorhombic RMnO₃ Perovskites: (R_0.667Mn_0.333)MnO₃ with R = Er–Lu

Abstract

Orthorhombic rare-earth trivalent manganites RMnO (R = Er-Lu) were self-doped with Mn to form (RMn)MnO compositions, which were synthesized by a high-pressure, high-temperature method at 6 GPa and about 1670 K from RO and MnO. The average oxidation state of Mn is 3+ in (RMn)MnO. 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 was confirmed by hard X-ray photoelectron spectroscopy measurements. Crystal structures were studied by synchrotron powder X-ray diffraction. (RMn)MnO crystallizes in space group Pnma with a = 5.50348(2) Å, b = 7.37564(1) Å, and c = 5.18686(1) Å for (LuMn)MnO at 293 K, and they are isostructural with the parent RMnO manganites. Compared with RMnO, (RMn)MnO exhibits enhanced Néel temperatures of about T = 106-110 K and ferrimagnetic or canted antiferromagnetic properties. Compounds with R = Er and Tm show additional magnetic transitions at about T = 9-16 K. (TmMn)MnO exhibits a magnetization reversal or negative magnetization effect with a compensation temperature of about 16 K.

Intrinsic Triple Order in A‐site Columnar‐Ordered Quadruple Perovskites: Proof of Concept

“…Moreover, negative magnetization or magnetization reversal was observed below about 10 K on the 100 Oe FCC curve. All these features resemble magnetic behaviours of (Ho 0.8 Mn 0.2 )MnO 3 (Figure S6b) and (Tm 0.667 Mn 0.333 )MnO 3 . Therefore, we conclude that the magnetic response in small magnetic fields is dominated by (Ho 0.8 Mn 0.2 )MnO 3 ferrimagnetic impurity.…”

Origin of negative magnetization phenomena in (Tm1−xMnx)MnDönni1, Pomjakushin2, Zhang3 et al. 2020Phys. Rev. BSelf Cite101100View full textAdd to dashboardCite

“…We note that in the case of disordered Tm moments, the 30% of Mn 2+ ions can produce a maximum average ordered moment of 1. study) has been studied in Ref. [23]. The difference between the specific heat C p /T curves of (Tm 0.667 Mn 0.333 )MnO 3 and (Lu 0.667 Mn 0.333 )MnO 3 corresponds to the magnetic entropy from Tm which is released up to the Curie temperature T C = 106 K of (Tm 0.667 Mn 0.333 )MnO 3 .…”

“…75%, 50%, and other doping levels can also produce disordered arrangements of cations at the A site and simple perovskite structures. We have recently found the formation of (R 1−x Mn x )MnO 3 solid solutions for R = Er-Lu with the GdFeO 3 -type Pnma structure [23,24]. Magnetic properties of (R 1−x Mn x )MnO 3 were significantly modified in comparison with undoped RMnO 3 perovskites due to the presence of magnetic Mn 2+ cations at the A sites even at the doping level of 20%, for example, ferrimagnetic structures were realized in (Lu 1−x Mn x )MnO 3 for 0.2 x 0.4 and magnetization reversal or negative magnetization effects [25] were observed in (Tm 0.667 Mn 0.333 )MnO 3 .…”

“…Single-phase hex-TmMnO 3 was synthesized from a stoichiometric mixture of Mn 2 O 3 and Tm 2 O 3 by annealing in air at ambient pressure at 1423 K for 80 h with several intermediate grindings. We note that the solubility limit of (Tm 1−x Mn x )MnO 3 solid solutions was reported to be x = 0.333 [23]. However, we selected the x = 0.3 sample for neutron diffraction studies to be sure that the sample is single phase as small variations in real synthesis conditions could slightly shift the solubility limit.…”

Magnetic structure and spin-flop transition in the A -site columnar-ordered quadruple perovskite TmMn3O6

“…Both impurity phases adopt long range magnetic order at low temperatures. Tm deficient TmMnO 3 undergoes three magnetic phase transitions at ∼110 K, ∼50 K and ∼20 K [31], and MnCO 3 magnetically orders below 34.5 K [32]. The Tm-poor TmMnO 3 magnetic structures are yet to be fully determined, so the respective intensities were fit using the Le Bail method.…”