(In_1−yMn_y)MnO₃ (1/9≤y≤1/3): Unusual Perovskites with Unusual Properties

Abstract

The perovskite-type ABO 3 structure is highly adaptive. There are hundreds of perovskite-type compounds.[1] Many of them have extremely important technological properties, for example BaTiO 3 , SrTiO 3 , SrRuO 3 , and Pb(Zr 1Àx Ti x )O 3 . Applications of perovskites range from use as catalysts or sensors to superconductors and ferromagnetic or ferroelectric materials.[1] Among perovskites, (doped) manganites LnMnO 3 (Ln = La-Lu) have been investigated a lot in the last decades because of the colossal magnetoresistance and orbital/charge ordering phenomena. [2,3] The discovery of multiferroic properties of LnMnO 3 (Ln = Tb-Lu) has attracted new interest to these systems. [4,5] LnMnO 3 (Ln = La-Lu) compounds are divided into two groups: perovskites LnMnO 3 (Ln = La-Dy) and hexagonal LnMnO 3 (Ln = Y, Ho-Lu). The perovskite modification can be stabilized for all members of LnMnO 3 (Ln = La-Lu) using a high-pressure synthesis or other methods. The magnetic phase diagram for perovskites LnMnO 3 (Ln = La-Lu) is well established, and there are two magnetic phases with longrange ordering and multiferroic properties for small Ln 3+ ions. [3][4][5] With decreasing radius of Ln 3+ ions, the Jahn-Teller distortion increases and the competition between nearestneighbor and next-nearest-neighbor interactions is enhanced.[3] Are there any possibilities to extend the existing phase diagram of LnMnO 3 ? The hexagonal modification is known for smaller ions, such as in ScMnO 3 , and InMnO 3 . [6,7] However, ScMnO 3 and InMnO 3 perovskites have never been reported, even though attempts to stabilize new phases of ScMnO 3 and InMnO 3 have been made. [8] Note that ScCrO 3 , [9] InCrO 3 , and InRhO 3 perovskites can be prepared at high pressure.[10] Indium-based perovskites have recently attracted attention as new room-temperature multiferroic materials. [11][12][13] Herein, we report on the stabilization of new perovskite oxides (In 1Ày Mn y )MnO 3 (1/9 y 1/3) using a high-pressure high-temperature technique. Not only is the discovery of new simple ABO 3 perovskites extremely rare these days, but (In 1Ày Mn y )MnO 3 perovskites are very unusual in a few ways. First, there is a significant number of Mn atoms at the A site of the perovskite structure together with Mn atoms at the B site, and the doping at the A site occurs by Mn 2+ ions. Second, (In 1Ày Mn y )MnO 3 crystallizes in the B-site-ordered structure owing to ordering of Mn All the observed reflections on the synchrotron XRD pattern of In 0.6 MnO 2.4 ((In 0.75 Mn 0.25 )MnO 3 ) could be indexed in a monoclinic system with a % 5.11, b % 5.31, c % 7.84 , and b % 92.198. Reflection conditions derived from the indexed reflections were h + l = 2n for h0l, h00, and 00l and k = 2n for 0k0, affording one possible space group P2 1 /n (No. 14, cell choice 2). The lattice parameters and space group correspond to the monoclinically distorted GdFeO 3 -type perovskite structure. Significant anisotropic broadening of reflections was observed in high-resolution synchrotron XRD data. [14] In gener...

Low‐Temperature Cationic Rearrangement in a Bulk Metal Oxide

“…[5,[28][29][30] Compared with the cationic re-distribution in spinel nanocrystals at moderate temperature (typically 350-600 8C), [12][13][14] electric potential-driven ionic motion in battery materials, [15,16] and ionic rearrangements in bulk oxides (typically above 600 8C), [10,11] O 6 octahedra in the ab-plane. This structural change relieves the lattice strain, as reflected by the degree of octahedral distortion (Figure 2 c, d and Table S5), and lowers the energy of the material.…”

“…[5,6] Displacive transitions can arise at relatively low temperatures, [7] while cationic rearrangements generally require high temperatures to overcome large energy barriers. [5,[8][9][10][11] Cationic rearrangements below 300 8 8Ch ave only been reported in nanocrystals, [12][13][14] or when driven by applied external electrical potential as in battery materials, [15,16] but not in bulk metal oxides by temperature alone.T he corundum-derived A 2 BB'O 6 family of compounds can incorporate transition metal ions at all of the cationic sites and adopt different cation order-disorder configurations,providing an ideal platform for materials engineering. [5,8,9,[17][18][19][20][21][22] Recently,t he polar roomtemperature (T C % 337 K) ferrimagnet Mn 2 FeMoO 6 ,h ereafter called phase I, was prepared by quenching to room temperature from 1350 8 8Ca tapressure of 8GPa.…”

Structure and magnetism of the A site scandium perovskite (Sc 0.94 Mn 0.06 )Mn 0.65 Ni 0.35 O 3 synthesized at high pressure

“…Both groups of crystallites appeared to be slightly scandium-deficient, with an Sc : (Mn/Ni) ratio of 0 3 , where M = Ge [17], Sn [18], Si [19], Ti [20] or V [21], and in the B site ordered (In 1−y Mn y )MnO 3 [22], where the B site ordered structure is realized through ordering of Mn 3+ refinement of synchrotron and neutron data was carried out using structural parameters from LuNiO 3 [24] in P2 distinct sites, they divided into two pairs of equivalent occupancies (table 2). The A site ordering corresponds to corrugated layers of the distinct Sc-only and 12% Mn/88% Sc A sites in the ac plane stacked along the b-axis (figure 2d).…”

Low‐Temperature Cationic Rearrangement in a Bulk Metal Oxide

“…Below 200 K, the limited data range does not allow any reasonable fit. [5,[28][29][30] Compared with the cationic re-distribution in spinel nanocrystals at moderate temperature (typically 350-600 8 8C), [12][13][14] electric potential-driven ionic motion in battery materials, [15,16] and ionic rearrangements in bulk oxides (typically above 600 8 8C), [10,11] the lattice-strain-driven cationic rearrangement in Mn 2 FeMoO 6 at such low temperatures (150-300 8 8C) is unique.I nt he Ni 3 Te O 6 -type phase I, the smaller cell volume is achieved by edge-sharing between the larger Mn 2+ (0.83 ) and smaller Fe 3+ (0.645 ) or Mo 5+ (0.61 ) [23] in the ab-plane.T he position swap between Mn2 and Fe within the face-sharing octahedral pairs result in the elongation of the c-axis,a nd alternating layers of the larger Mn1 2+ O 6 -Mn2 2+ O 6 edge-sharing octahedra with the smaller Fe 3+ O 6 -Mo 5+ O 6 octahedra in the ab-plane.T his structural change relieves the lattice strain, as reflected by the degree of octahedral distortion (Figure 2c,d and Table S5), and lowers the energy of the material. [27] Thec orundum-derived crystal structures under high pressure can crystallize in the structural type of the smallest possible cell volume by the arrangement of edge-sharing octahedra between the larger and smaller cations in the abplane,a tacost of lattice strain owing to ion size mismatch.…”

“…[1][2][3][4] One common strategy to control the cationic distribution and environment for desired applications in bulk oxides is to manipulate the displacive transitions (polyhedral distortions and cooperative tilting/rotation), or the cationic rearrangements. [5,[8][9][10][11] Cationic rearrangements below 300 8 8Ch ave only been reported in nanocrystals, [12][13][14] or when driven by applied external electrical potential as in battery materials, [15,16] but not in bulk metal oxides by temperature alone.T he corundum-derived A 2 BB'O 6 family of compounds can incorporate transition metal ions at all of the cationic sites and adopt different cation order-disorder configurations,providing an ideal platform for materials engineering. [5,[8][9][10][11] Cationic rearrangements below 300 8 8Ch ave only been reported in nanocrystals, [12][13][14] or when driven by applied external electrical potential as in battery materials, [15,16] but not in bulk metal oxides by temperature alone.T he corundum-derived A 2 BB'O 6 family of compounds can incorporate transition metal ions at all of the cationic sites and adopt different cation order-disorder configurations,providing an ideal platform for materials engineering.…”