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ScRhO3 and InRhO3 perovskites were synthesized at a high pressure of 6 GPa and a high temperature of 1500 K. Crystal structures of ScRhO3 and InRhO3 were studied with synchrotron X-ray powder diffraction at 293 and 134 K. ScRhO3 and InRhO3 have a rarely observed monoclinic superstructure of the GdFeO3-type structure (space group P21/n, a = 7.45660 Å, b = 7.43524 Å, c = 7.52191 Å, and β = 93.2930° for ScRhO3 and a = 7.59020 Å, b = 7.58377 Å, c = 7.59010 Å, and β = 91.4154° for InRhO3 at 293 K). InRhO3 has pseudo-orthorhombic lattice parameters of a = 10.8658 Å, b = 7.5837 Å, and c = 10.6006 Å. ScRhO3 and InRhO3 are nonmagnetic, and no phase transitions were detected between 2 and 873 K. Crystallographic trends and distortions of ScRhO3, InRhO3, and RRhO3 (R = rare earths, Y, and Bi) are discussed.

The crystal structure of the layered cobalt oxyfluoride Sr(2)CoO(3)F synthesized under high-pressure and high-temperature conditions has been determined from neutron powder diffraction and synchrotron powder diffraction data collected at temperatures ranging from 320 to 3 K. This material adopts the tetragonal space group I4/mmm over the measured temperature range and the crystal structure is analogous to n = 1 Ruddlesden-Popper type layered perovskite. In contrast to related oxyhalide compounds, the present material exhibits the unique coordination environment around the Co metal center: coexistence of square pyramidal coordination around Co and anion disorder between O and F at the apical sites. Magnetic susceptibility and electrical resistivity measurements reveal that Sr(2)CoO(3)F is an antiferromagnetic insulator with the Néel temperature T(N) = 323(2) K. The magnetic structure that has been determined by neutron diffraction adopts a G-type antiferromagnetic order with the propagation vector k = (1/2 1/2 0) with an ordered cobalt moment μ = 3.18(5) μ(B) at 3 K, consistent with the high spin electron configuration for the Co(3+) ions. The antiferromagnetic and electrically insulating states remain robust even against 15%-O substation for F at the apical sites. However, applying pressure exhibits the onset of the metallic state, probably coming from change in the electronic state of square-pyramidal coordinated cobalt., (© 2012 American Chemical Society)

Single-crystal Ca(10)(Pt(4)As(8))(Fe(1.8)Pt(0.2)As(2))(5) superconducting (SC) nanowhiskers with widths down to hundreds of nanometers were successfully grown in a Ta capsule in an evacuated quartz tube by a flux method. Magnetic and electrical properties measurements demonstrate that the whiskers have excellent crystallinity with critical temperature of up to 33 K, upper critical field of 52.8 T, and critical current density of J(c) of 6.0 × 10(5) A/cm(2) (at 26 K). Since cuprate high-T(c) SC whiskers are fragile ceramics, the present intermetallic SC whiskers with high T(c) have better opportunities for device applications. Moreover, although the growth mechanism is not understood well, the technique can be potentially useful for growth of other whiskers containing toxic elements., (© 2012 American Chemical Society)

Low-temperature vacuum reduction was used for the preparation of the oxygen-deficient BiMnO(2.81) sample in a bulk form from stoichiometric BiMnO(3). The transformation occurs in vacuum better than 10(-3) Pa at a narrow temperature range of 570-600 K. The structure of the new phase was analyzed using synchrotron X-ray powder diffraction data. BiMnO(2.81) crystallizes in a perovskite-type cubic structure (space group I-43d) with a = 15.88552(5) Å corresponding to a 4a(p) superstructure, where a(p) is the parameter of the cubic perovskite subcell. Oxygen vacancies are ordered, and one oxygen site in BiMnO(2.81) is completely vacant, resulting in MnO(5) pyramids. BiMnO(2.81) is rather unstable in air and slowly restores its oxygen content even at room temperature., (© 2011 American Chemical Society)

LiNbO(3) (LN), corundum (cor), and hexagonal (hex) phases of (In(1-x)M(x))MO(3) (x = 0.143; M = Fe(0.5)Mn(0.5)) were prepared. Their crystal structures were investigated with synchrotron X-ray powder diffraction, and their properties were studied by differential thermal analysis, magnetic measurements, and Mössbauer spectroscopy. The LN-phase was prepared at high pressure of 6 GPa and 1770 K; it crystallizes in space group R3c with a = 5.25054(7) Å, c = 13.96084(17) Å, and has a long-range antiferromagnetic ordering near T(N) = 270 K. The cor- and hex-phases were obtained at ambient pressure by heating the LN-phase in air up to 870 and 1220 K, respectively. The cor-phase crystallizes in space group R-3c with a = 5.25047(10) Å, c = 14.0750(2) Å, and the hex-phase in space group P6(3)/mmc with a = 3.34340(18) Å, c = 11.8734(5) Å. T(N) of the cor-phase is about 200 K, and T(N) of the hex-phase is about 140 K. During irreversible transformations of LN-(In(1-x)M(x))MO(3) with the (partial) cation ordering, the In(3+), Mn(3+), and Fe(3+) cations become completely disordered in one crystallographic site of the corundum structure, and then they are (partially) ordered again in the hex-phase. LN-(In(1-x)M(x))MO(3) exhibits a reversible transformation to a perovskite GdFeO(3)-type structure (space group Pnma; a = 5.2946(3) Å, b = 7.5339(4) Å, c = 5.0739(2) Å at 10.3 GPa) at room temperature and pressure of about 5 GPa.

Solid solutions InMn(1-x)Ga(x)O(3) (0 ≤ x ≤ 1) have been investigated using magnetic, dielectric, specific heat, differential scanning calorimetry (DSC), and high-temperature powder synchrotron X-ray diffraction (HT-SXRD) measurements. It was found that samples with 0.5 ≤ x ≤ 1 crystallize in space group P6(3)/mmc with a ~ 3.32 Å and c ~ 11.9 Å, and samples with 0.0 ≤ x ≤ 0.4 crystallize in space group P6(3)cm with a ~ 5.8 Å and c ~ 11.6 Å at room temperature. HT-SXRD data revealed the existence of a P6(3)cm-to-P6(3)/mmc phase transition at about 480 K in InMn(0.6)Ga(0.4)O(3) and at 950 K in InMn(0.7)Ga(0.3)O(3). However, no dielectric, phonon, second-harmonic-generation, or DSC anomalies were found to be associated with these phase transitions. The phase transition should be improper ferroelectric from the symmetry point of view, but the above-mentioned experimental facts, together with the absence of ferroelectric hysteresis loops, revealed no evidence for ferroelectricity in the low-temperature P6(3)cm structure. We suggest that InMn(1-x)Ga(x)O(3) corresponds to a nonferroelectric phase of hexagonal RMnO(3) with P6(3)cm symmetry. The antiferromagnetic phase-transition temperature decreases from 118 K for x = 0 to 105 K for x = 0.1 and 73 K for x = 0.2, and no long-range magnetic ordering could be found for x ≥ 0.3. Specific heat anomalies associated with short-range magnetic ordering were observed for 0.0 ≤ x ≤ 0.5. InMn(1-x)Ga(x)O(3) with small Mn contents (0.8 ≤ x ≤ 0.98) has a bright-blue color.

The effects of oxygen content on the structural, physical, and chemical properties of Bi(3)Mn(3)O(11) with KSbO(3)-type structure have been investigated. It was found that the oxygen content in Bi(3)Mn(3)O(11+delta) can vary over a wide delta range, keeping the same cubic structure (space group Pn3, a = 9.12172(5) A for delta = -0.5, a = 9.13784(8) A for delta = 0, and a = 9.09863(7) A for delta = 0.6) and semiconducting properties of the material. At the same time, magnetic properties change from true antiferromagnetic with T(N) = 45 K for delta = -0.5 to true ferromagnetic with T(C) = 307 K for delta = +0.6. Bi(3)Mn(3)O(11) (delta = 0) shows ferrimagnetic-like properties with T(C) = 150 K and features typical for a re-entrant spin-glass below 30 K. Noticeable changes of the magnetic transition temperature and magnetism in Bi(3)Mn(3)O(11+delta) with delta can be compared with changes of the magnetic and electronic properties of LaMnO(3+delta), BiMnO(3+delta), high-temperature copper superconductors (e.g., YBa(2)Cu(3)O(7+delta)), and other cuprates. Bi(3)Mn(3)O(11.6) shows a new record high T(C) among insulating/semiconducting true ferromagnets. Our results demonstrate that the oxygen content can vary for the same cation composition in KSbO(3)-type materials, and the oxygen content can be increased up to BiMnO(3.867) (Bi(3)Mn(3)O(11.6)).

The structural and electronic properties of BiCoO(3) under high pressure have been investigated. Synchrotron X-ray and neutron powder diffraction studies show that the structure changes from a polar PbTiO(3) type to a centrosymmetric GdFeO(3) type above 3 GPa with a large volume decrease of 13% at room temperature revealing a spin-state change. The first-order transition is accompanied by a drop of electrical resistivity. Structural results show that Co(3+) is present in the low spin state at high pressures, but X-ray emission spectra suggest that the intermediate spin state is present. The pressure-temperature phase diagram of BiCoO(3) has been constructed enabling the transition temperature at ambient pressure to be estimated as 800-900 K.

Crystals of the newly synthesized compound Ca(3)LiOsO(6) were grown by a flux method using LiCl and KCl, followed by single-crystal X-ray diffraction (XRD), low-temperature powder XRD, and measurements of ac and dc magnetic susceptibility and specific heat. The data indicate that Ca(3)LiOsO(6) has a fully opened electronic gap with an antiferromagnetic ordered state, consistent with suggestions from the first-principles study. The observed magnetic transition temperature is 117 K, too high to be caused only by a direct spin-spin interaction. It appears that the original superexchange magnetic path Os-O-Os is absent; thus, the extended superexchange path (Os-O)-(O-Os) can be expected to be responsible for the 117 K magnetic order. If this is true, Ca(3)LiOsO(6) would be highly valuable to study the nature of extended superexchange magnetic interactions in solids.

Crystal and magnetic structures of BiMnO(3+delta) (delta = 0.03, 0.08, and 0.14) have been determined by the Rietveld method from neutron diffraction data at 8-10 and 290 K. BiMnO(3.03) (= Bi(0.99)Mn(0.99)O(3)) crystallizes in a monoclinic system (the refinement was performed in space group C2/c; Z = 8; a = 9.5313(3) A, b = 5.57791(17) A, c = 9.7375(4) A, beta = 108.951(2) degrees at 290 K). BiMnO(3.08) (= Bi(0.974)Mn(0.974)O(3)) crystallizes in space group P2(1)/c (Z = 8; a = 9.5565(4) A, b = 5.51823(16) A, c = 9.7051(4) A, beta = 109.442(3) degrees at 290 K). It was found that Mn vacancies are localized mainly in one Mn site (among three sites) in Bi(0.974)Mn(0.974)O(3). Vacancy-ordering and charge-ordering scenarios are suggested as possible reasons for the crystal symmetry change compared with Bi(0.99)Mn(0.99)O(3). BiMnO(3.03) and BiMnO(3.08) are ferromagnetic below T(C) = 82 and 68 K, respectively, with magnetic moments along the monoclinic b axes. Refined magnetic moments at 10 K are 2.88(2)micro(B) in BiMnO(3.03) and 2.33(2)micro(B) in BiMnO(3.08). BiMnO(3.14) (= Bi(0.955)Mn(0.955)O(3)) crystallizes in an orthorhombic system (space group Pnma; Z = 4; a = 5.5136(4) A, b = 7.8069(8) A, and c = 5.5454(5) A at 290 K), and its structure is similar to that of LaMnO(3.11)-LaMnO(3.15). No magnetic reflections were found in BiMnO(3.14) down to 8 K, in agreement with its spin-glass magnetic state. Magnetic and chemical properties of BiMnO(3+delta) (0.02 < or = delta < or = 0.14) have also been investigated and compared with those of LaMnO(3+delta). Systematic changes of magnetic parameters in BiMnO(3+delta) were found to depend on delta.

A new compound, Bi(3)Mn(3)O(11), with a KSbO(3)-type structure was prepared using a high-pressure technique. Its structural, chemical, and magnetic properties have been investigated. Bi(3)Mn(3)O(11) was shown to be a ferrimagnet with rather high T(C) despite the random distribution of manganese ions with different oxidation states in one site. Bi(3)Mn(3)O(11) gradually loses oxygen on heating forming several phases with the same structure but with different magnetic properties. These findings may revive interest in the KSbO(3) family of compounds, which is rather adaptive considering the cation variations and oxygen content.

A high-quality polycrystalline sample of the correlated 4d post-perovskite CaRhO(3) (Rh(4+): 4d(5), S(el) = 1/2) was attained under a moderate pressure of 6 GPa. Since the post-perovskite is quenchable at ambient pressure/temperature, it can be a valuable analogue of the post-perovskite MgSiO(3) (stable higher than 120 GPa and unstable at ambient pressure), which is a significant key material in earth science. The sample was subjected for measurements of charge-transport and magnetic properties. The data clearly indicate it goes into an antiferromagnetically ordered state below approximately 90 K in an unusual way, in striking contrast to what was observed for the perovskite phase. The post-perovskite CaRhO(3) offers future opportunities for correlated electrons science as well as earth science.

High-pressure structural properties of perovskite-type BiMnO(3) have been investigated by synchrotron X-ray powder diffraction at room temperature. A new monoclinic phase having P2(1)/c symmetry was found between about 1.5 and 5.5 GPa. Above 8 GPa, the orthorhombic GdFeO(3)-type phase (space group Pnma) is stable. The crystal structure of BiMnO(3) at 8.6 GPa and room temperature was investigated (a = 5.5132(3) A, b = 7.5752(3) A, c = 5.4535(3) A). The orthorhombic phase of BiMnO(3) has an orbital order similar to LaMnO(3) but with a different arrangement of orbitals in the ac plane. High-pressure room-temperature behavior of BiMnO(3) differs from high-temperature behavior at ambient pressure in comparison with BiCrO(3) and BiScO(3). These findings may open new directions in investigation of BiMnO(3).

The incommensurate modulated crystal structure of the new misfit-layer calcium cobalt oxide (Ca0.85OH)2alphaCoO2 was investigated using a superspace-group formalism with synchrotron X-ray diffraction data. The compound is a kind of composite crystal that consists of two interpenetrating subsystems, [CoO2]infinity layers containing triangular lattices formed by edge-sharing CoO6 octahedra, separated from each other by [2Ca0.85OH]infinity double-layered rock-salt-type slabs. Both the subsystems are monoclinic lattices with the unit cell parameters, a1 = 2.8180(4) A, b = 4.8938(6) A, c = 8.810(1) A, alpha0 = 95.75(3) degrees , and alpha(=|q|=a1/a2) = 0.57822(8), viz., a2 = 4.8736 A, with Z = 2. A possible superspace group is C2/m(alpha10)s0-C21/m(alpha(-1)10) for the respective subsystems. The atomic positions deviate from the average positions of the fundamental structure due to the incommensurable periodic interaction between the subsystems. A significant structural modulation was found in the [2Ca0.85OH] subsystem, whereas the modulation in the [CoO2] subsystem is less than in [2Ca0.85OH], due to the tight bonding of the close-packed CoO6 octahedra. The degree of modulation in the CoO2 layers, i.e., the potential modulation, is almost the same as those of other compounds of the misfit-layer cobalt oxides. Flattened CoO6 octahedra indicate hole doping into the CoO2 layers. The [2Ca0.85OH] blocks act as the charge reservoir layers, and the defect Ca ions are presumably the source of the holes.

Single-phased powder BiCrO(3) sample was prepared at 6 GPa and 1653 K. Its magnetic properties were investigated by dc/ac magnetization, magnetic relaxation, and specific heat measurements. Four anomalies of magnetic origin were found near 40, 75, 109, and 111 K. The long-range antiferromagnetic order with weak ferromagnetism occurs at T(N) = 109 K. The ac susceptibilities showed that the transition near T(N) is a two-step transition. Additional frequency-independent broad anomalies were observed on the real part of the ac susceptibilities near 75 K, likely, caused by the change in the magnetic easy axis. The dc magnetic susceptibilities also had anomalies at 75 K, and the isothermal magnetization curves and relaxation curves changed their behavior below 75 K. Below 40 K, frequency-dependent anomalies with very large temperature shifts were observed on both the real and imaginary parts of the ac susceptibilities. The monoclinic-to-orthorhombic structural phase transition near 420 K was investigated by magnetization and differential scanning calorimetry measurements.

Synthetic mineral libethenite Cu(2)PO(4)OH was prepared by the hydrothermal method, and its structure at 200 K was refined by single-crystal X-ray diffraction. The structure of Cu(2)PO(4)OH is built up from Cu2(2)O(6)(OH)2 dimers of edge-sharing Cu2O(4)(OH) trigonal bipyramids and [Cu1(2)O(6)(OH)(2)] proportional chains of edge-sharing Cu1O(4)(OH)(2) octahedra. Magnetic properties of Cu(2)PO(4)OH were investigated by magnetic susceptibility, magnetization, and specific heat measurements. Cu(2)PO(4)OH is a spin-gap system with a spin gap of about 139 K. It was shown by spin dimer analysis that, to a first approximation, the magnetic structure of Cu(2)PO(4)OH is described by an isolated square-spin cluster model defined by the Cu1-O-Cu2 superexchange J with Cu1...Cu2 = 3.429 A. The fitting analysis of the magnetic susceptibility data with a square-spin cluster model results in J/k(B) = 138 K. Specific heat data show that Cu(2)PO(4)OH does not undergo a long-range magnetic ordering down to 1.8 K. We also report vibrational properties studied with Raman spectroscopy and the thermal stability of Cu(2)PO(4)OH.

Solid solutions BiMn1-xMxO3 with M=Al, Sc, Cr, Fe, and Ga and 0

Structural properties of polycrystalline single-phased BiMnO3 samples prepared at 6 GPa and 1383 K have been studied by selected area electron diffraction (SAED), convergent beam electron diffraction (CBED), and the Rietveld method using neutron diffraction data measured at 300 and 550 K. The SAED and CBED data showed that BiMnO3 crystallizes in the centrosymmetric space group C2/c at 300 K. The crystallographic data are a = 9.5415(2) A, b = 5.61263(8) A, c = 9.8632(2) A, beta = 110.6584(12) degrees at 300 K and a = 9.5866(3) A, b = 5.59903(15) A, c = 9.7427(3) A, beta = 108.601(2) degrees at 550 K, Z = 8, space group C2/c. The analysis of Mn-O bond lengths suggested that the orbital order present in BiMnO3 at 300 K melts above TOO = 474 K. The phase transition at 474 K is of the first order and accompanied by a jump of magnetization and small changes of the effective magnetic moment and Weiss temperature, mueff = 4.69 microB and theta = 138.0 K at 300-450 K and mueff = 4.79 microB and theta = 132.6 K at 480-600 K.

Magnetic and specific heat measurements were performed in a single-phased powder BiMnO3 sample prepared at 6 GPa and 1383 K. The imaginary part of the ac susceptibilities showed strong frequency dependence below the ferromagnetic Curie temperature of 98 K. The relaxation measurements revealed time-dependent magnetic properties below 98 K. These data indicate the appearance of a "spin-glass-like" state in BiMnO3. Specific heat measurements showed the existence of ferromagnetic spin waves. However, no simple term Cm [directly proportional] T3/2 was found indicating an unconventional behavior of the magnetic specific heat. The Debye temperature was estimated to be 410 K using isostructural compounds BiScO3 and BiCrO3.

A new form of LiMn2O4 is reported. The structure is the CaFe2O4-type and 6% denser than the spinel. The structure transformation was achieved by heating at 6 GPa. Analysis of the neutron diffraction pattern confirmed an average of the structure; the unit cell was orthorhombic at a = 8.8336(5) angstroms, b = 2.83387(18) angstroms, and c = 10.6535(7) angstroms (Pnma). Electron diffraction patterns indicated an order of superstructure 3a x b x c, which might be initiated by Li vacancies. The exact composition is estimated at Li(0.92)Mn2O4 from the structure analysis and quantity of intercalated Li. The polycrystalline CaFe2O4-type compound showed semiconducting-like characters over the studied range above 5 K. The activation energy was reduced to approximately 0.27 eV from approximately 0.40 eV at the spinel form, suggesting a possible enhancement of hopping mobility. Magnetic and specific-heat data indicated a magnetically glassy transition at approximately 10 K. As the CaFe2O4-type transition was observed for the mineral MgAl2O4, hence the new form of the lithium manganese oxide would provide valuable opportunities to study not only the magnetism of strongly correlated electrons but also the thermodynamics of the phase transition in the mantle.

With neutron powder diffraction, electron diffraction, and second-harmonic generation, we have shown that BiScO3 has a structure closely related to that of multiferroic BiMnO3, but BiScO3 crystallizes in the centrosymmetric space group of C2/c. These results bring up a question about the origin of ferroelectricity in BiMnO3. BiScO3 may serve as a model system to understand the role of Mn3+ ions in the ferroelectricity of BiMnO3.