Abstract:We synthesize CdMn7O12 and SrMn7-xFexO12 (x = 0, 0.08, and 0.5) perovskites under high pressure (6 GPa) and high temperature (1373-1573 K) conditions and investigate their structural, magnetic, dielectric, and ferroelectric properties. CdMn7O12 and SrMn7O12 are isostructural with CaMn7O12: space group R3̅ (No. 148), Z = 3, and lattice parameters a = 10.45508(2) Å and c = 6.33131(1) Å for CdMn7O12 and a = 10.49807(1) Å and c = 6.37985(1) Å for SrMn7O12 at 295 K. There is a structural phase transition at 493 K i… Show more
“…19 Using the present results, we showed that they also have low-temperature structural modulations. This behaviour is difficult to rationalize qualitatively.…”
Section: Discussionsupporting
confidence: 64%
“…The observed DSC anomalies are intrinsic as confirmed by low-temperature synchrotron XRPD results given below. A baseline of the DSC curves can be more or less unambiguously determined in PbMn 7 O 12 , and the estimated enthalpy of the transition is about 0.16 J/g; this value is about 40 times smaller that the enthalpy of the R-3-to-Im-3 transition (6.6 J/g) 19. Iron doping had noticeable effects on the DSC anomalies at T CO and T OO reducing the phase transition temperatures and significantly broadening the DSC effects.…”
mentioning
confidence: 93%
“…(AA' 3 )B 4 O 12 materials show many interesting physical and chemical properties, 4 for example, low-field magnetoresistence, 11 heavy Fermion physics, 12 multiferroic behaviour, 13,14 and high-performance catalytic activity. 15 When A' = B = Mn, an interesting family of materials is formed, AMn 7 O 12 , with (A = Mn, 9 Na, [16][17][18] Ca, Cd, 16,19 Sr, 16,19 Pb, 20 La, 16,21 Pr, 22 Nd, 16 and Bi 23,24 ). Many members of this family were discovered in the 1970s by Marezio et al 16,17 and investigated a lot because of complex magnetic-order, orbital-order, and charge-order transitions.…”
Section: Introductionmentioning
confidence: 99%
“…The Fe2 doublet corresponds to Fe 3+ ions located at the Mn3 site having almost symmetrical octahedral coordination and occupied by Mn 4+ ions (Table 1). 19,40,41 In the P-3 phase of CdMn 7 O 12 , the Mn2 site (9d in R-3) will split into 3f and 6g, and the Mn3 site (3b in R-3) -into 1b and 2d. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 9 Temperature dependence of isomer shifts, δ 1 (T) and δ 2 (T), for all the samples is almost linear between 80 and 300 K ( Figure S5) without any anomalies (e.g., changes in slope) indicating the absence of any changes in the lattice dynamics.…”
Structural phase transitions in CdMn 7 O 12 , CaMn 7 O 12 , SrMn 7 O 12 , and PbMn 7 O 12 perovskites are investigated by synchrotron X-ray powder diffraction between 113 and 583 K, differential scanning calorimetry (DSC), and Mössbauer spectroscopy on 57 Fe-doped samples. DSC is used to determine phase transition temperatures (T OO ).All the compounds crystallize in space group R-3 at room temperature. An incommensurate structural modulation is observed below T OO = 265 K in SrMn 7 O 12 with a propagation vector q = (0, 0, 0.9235) at 113 K, similar to the already-reported case of CaMn 7 O 12 (with T OO = 258 K and q = (0, 0, 0.9215) at 113 K). However, superstructure reflections of SrMn 7 O 12 are significantly weaker than those of CaMn 7 O 12 . On the other hand, a commensurate structural transition is found in CdMn 7 O 12 below T OO = 254 K and in PbMn 7 O 12 below T OO = 294 K; the transition can be described as from space group R-3 to space group P-3 with the same unit cell dimensions (a = 10.43306(2) Å and c = 6.33939(1) Å in CdMn 7 O 12 at 113 K). CdMn 7 O 12 shows quite strong superstructure reflections at 113 K, while PbMn 7 O 12 has extremely small superstructure reflections. Below T OO , the c lattice parameter of all the compounds increases with decreasing temperature (down to 113 K). Mössbauer spectroscopy shows that quadrupole splitting noticeably increases below T OO ; and we quantitatively explain this increase in CaMn 7 O 12 by structural modulations. Structure parameters of the R-3 modification and high-temperature Im-3 modification of CaMn 7 O 12 and PbMn 7 O 12 are also reported.
“…19 Using the present results, we showed that they also have low-temperature structural modulations. This behaviour is difficult to rationalize qualitatively.…”
Section: Discussionsupporting
confidence: 64%
“…The observed DSC anomalies are intrinsic as confirmed by low-temperature synchrotron XRPD results given below. A baseline of the DSC curves can be more or less unambiguously determined in PbMn 7 O 12 , and the estimated enthalpy of the transition is about 0.16 J/g; this value is about 40 times smaller that the enthalpy of the R-3-to-Im-3 transition (6.6 J/g) 19. Iron doping had noticeable effects on the DSC anomalies at T CO and T OO reducing the phase transition temperatures and significantly broadening the DSC effects.…”
mentioning
confidence: 93%
“…(AA' 3 )B 4 O 12 materials show many interesting physical and chemical properties, 4 for example, low-field magnetoresistence, 11 heavy Fermion physics, 12 multiferroic behaviour, 13,14 and high-performance catalytic activity. 15 When A' = B = Mn, an interesting family of materials is formed, AMn 7 O 12 , with (A = Mn, 9 Na, [16][17][18] Ca, Cd, 16,19 Sr, 16,19 Pb, 20 La, 16,21 Pr, 22 Nd, 16 and Bi 23,24 ). Many members of this family were discovered in the 1970s by Marezio et al 16,17 and investigated a lot because of complex magnetic-order, orbital-order, and charge-order transitions.…”
Section: Introductionmentioning
confidence: 99%
“…The Fe2 doublet corresponds to Fe 3+ ions located at the Mn3 site having almost symmetrical octahedral coordination and occupied by Mn 4+ ions (Table 1). 19,40,41 In the P-3 phase of CdMn 7 O 12 , the Mn2 site (9d in R-3) will split into 3f and 6g, and the Mn3 site (3b in R-3) -into 1b and 2d. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 9 Temperature dependence of isomer shifts, δ 1 (T) and δ 2 (T), for all the samples is almost linear between 80 and 300 K ( Figure S5) without any anomalies (e.g., changes in slope) indicating the absence of any changes in the lattice dynamics.…”
Structural phase transitions in CdMn 7 O 12 , CaMn 7 O 12 , SrMn 7 O 12 , and PbMn 7 O 12 perovskites are investigated by synchrotron X-ray powder diffraction between 113 and 583 K, differential scanning calorimetry (DSC), and Mössbauer spectroscopy on 57 Fe-doped samples. DSC is used to determine phase transition temperatures (T OO ).All the compounds crystallize in space group R-3 at room temperature. An incommensurate structural modulation is observed below T OO = 265 K in SrMn 7 O 12 with a propagation vector q = (0, 0, 0.9235) at 113 K, similar to the already-reported case of CaMn 7 O 12 (with T OO = 258 K and q = (0, 0, 0.9215) at 113 K). However, superstructure reflections of SrMn 7 O 12 are significantly weaker than those of CaMn 7 O 12 . On the other hand, a commensurate structural transition is found in CdMn 7 O 12 below T OO = 254 K and in PbMn 7 O 12 below T OO = 294 K; the transition can be described as from space group R-3 to space group P-3 with the same unit cell dimensions (a = 10.43306(2) Å and c = 6.33939(1) Å in CdMn 7 O 12 at 113 K). CdMn 7 O 12 shows quite strong superstructure reflections at 113 K, while PbMn 7 O 12 has extremely small superstructure reflections. Below T OO , the c lattice parameter of all the compounds increases with decreasing temperature (down to 113 K). Mössbauer spectroscopy shows that quadrupole splitting noticeably increases below T OO ; and we quantitatively explain this increase in CaMn 7 O 12 by structural modulations. Structure parameters of the R-3 modification and high-temperature Im-3 modification of CaMn 7 O 12 and PbMn 7 O 12 are also reported.
“…It could be due to extrinsic factors such as space trapped charges at grain boundaries. We note that a broad and high pyroelectric peak was often reported in the quadruple perovskite manganites such as CaMn 7 O 12 , and its origin is quite controversial 27,34–44 .Fig. 5Spin-induced ferroelectricity in the binary perovskite Mn 2 O 3 .…”
The ABO3 perovskite oxides exhibit a wide range of interesting physical phenomena remaining in the focus of extensive scientific investigations and various industrial applications. In order to form a perovskite structure, the cations occupying the A and B positions in the lattice, as a rule, should be different. Nevertheless, the unique binary perovskite manganite Mn2O3 containing the same element in both A and B positions can be synthesized under high-pressure high-temperature conditions. Here, we show that this material exhibits magnetically driven ferroelectricity and a pronounced magnetoelectric effect at low temperatures. Neutron powder diffraction revealed two intricate antiferromagnetic structures below 100 K, driven by a strong interplay between spin, charge, and orbital degrees of freedom. The peculiar multiferroicity in the Mn2O3 perovskite is ascribed to a combined effect involving several mechanisms. Our work demonstrates the potential of binary perovskite oxides for creating materials with highly promising electric and magnetic properties.
The oxygen evolution reaction (OER) is one of the essential energy conversion reactions for hydrogen production. In quadruple perovskite oxides AA’3B4O12 (A=Ca, Sr, A’=Cu, Mn and B=3d metals), the new reaction mechanism of O−O bond formation between adsorbed oxygen species at adjacent A’‐B sites has been proposed in recent studies. This idea of multiple transition metals working together to form an active site, rather than a single active site, is appealing, but has not been systematically investigated so far. This study examined catalytic OER performances of CaMn7O12 quadruple perovskite oxides with precisely controlled Mn(A′)−Mn(B) distance by doping with Sr, Cu and Al. The crystal structure and the state of cations and O were investigated through XRD with Rietveld refinement and X‐ray absorption spectroscopy. The OER catalytic activity is clearly correlated with the distance of Mn(A’)−Mn(B) while both eg state of Mn and O 2p band center unchanged. The shrinkage of the A’‐B distance affects the stability of O−O bond on A’‐B site and accelerates OER kinetics.
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