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Chalcogenide-containing compounds have been widely studied as infrared nonlinear optical (NLO) materials. However, they have never been applied in the ultraviolet (UV) region owing to the high energy levels of chalcogen anions, leading to band gap narrowing. We report the synthesis of a new UV NLO oxysulfide La3 Ga3 Ge2 S3 O10 with an exceptionally wide band gap of 4.70 eV due to from the unique anion-ordered frameworks comprising 1D 1∞ [(Ga3/5 Ge2/5 )3 S3 O3 ] triangular tubes and 0D (Ga3/5 Ge2/5 )2 O7 dimers of corner-sharing (Ga/Ge)S2 O2 and (Ga/Ge)O4 tetrahedra, respectively. Second harmonic generation (SHG) measurements revealed that La3 Ga3 Ge2 S3 O10 was phase matchable with twice the SHG response of KH2 PO4 . The results of theoretical calculations suggest that the strong SHG response is mainly attributable to the S-3p and O-2p orbitals in the occupied states. The anion-directed band-gap engineering may give insights into the application of NLO oxychalcogenides in the UV regions.

A Polycrystalline sample of Pb2NiOsO6 was synthesized by high-pressure (6 GPa) and high-temperature (1575 K) conditions. Pb2NiOsO6 crystallizes in a monoclinic double perovskite structure with a centrosymmetric space group P21/n at room temperature. Pb2NiOsO6 is metallic down to 2 K and shows a single antiferromagnetic (AFM) transition at TN = 58 K. Pb2NiOsO6 is a new example of a metallic and antiferromagnetic oxide with three-dimensional connectivity. Neutron powder diffraction and first-principle calculation studies indicate that both Ni and Os moments are ordered below TN and the antiferromagnetic magnetic order breaks inversion symmetry. This loss of inversion symmetry driven by antiferromagnetic order is unusual in metallic systems and the 3d-5d double-perovskite oxides represent a new class of noncentrosymmetric AFM metallic oxides.

ABO3 perovskites have a number of ferroelectric instabilities resulting in varieties of long-range and short-range polar distortions. On the other hand, polar distortions are very limited in quadruple perovskites AA′3B4O12 and A2A′A′′B4O12. Here we showed that R2MnMn(MnTi3)O12 oxides, belonging to a family of A-site columnar-ordered quadruple perovskites, exhibit relaxor-like ferroelectric properties slightly below room temperature. They were synthesized by a high-pressure high-temperature method for R = Nd, Eu, and Gd at about 6 GPa and 1570 K. At room temperature they crystallize in centrosymmetric space group P42/nmc (no. 137), and their crystal structures were studied by synchrotron powder X-ray diffraction. They exhibit broad dielectric anomalies just below room temperature with characteristic frequency-dependent features of the relaxor ferroelectric behavior. P–E loop measurements at 77 K confirmed ferroelectricity for R = Nd and Eu. Magnetic and specific heat measurements showed the presence of long-range ferrimagnetic transitions below 20 K (R = Nd), 30 K (R = Eu), and 42 K (R = Gd). Additional specific heat anomalies were observed below about 5 K for R = Nd and Gd probably due to the involvement of rare-earth cations in long-range orderings. The coexistence of ferrimagnetic transitions and relaxor-like ferroelectric properties make R2MnMn(MnTi3)O12 perovskites multiferroic materials.

NaOsO3 has recently attracted significant attention for the strong coupling between its electronic band structure and magnetic ordering. Here, we used time-resolved magnetic x-ray diffraction to determine the timescale of the photoinduced antiferromagnetic dynamics in NaOsO3. Our measurements are consistent with a sub-100 fs melting of the antiferromagnetic long-range order that occurs significantly faster than the lattice dynamics as monitored by the transient change in intensity of selected Bragg structural reflections, which instead show a decrease of intensity on a timescale of several ps.

The formation of NaRMn2Ti4O12 compounds (R = rare earth) under high pressure (about 6 GPa) and high temperature (about 1750 K) conditions was studied. Such compounds with R = Sm, Eu, Gd, Dy, Ho, Y ...

Single crystals of a new germanium oxysulfide La4(GeS2O2)3 were grown out of a BaCl2-CaCl2 eutectic flux, and the crystal structure was determined via single-crystal X-ray diffraction. Ivory-white ...

Polycrystalline Sr3OsO6, which is an ordered double-perovskite insulator, is synthesized via solid-state reaction under high-temperature and high-pressure conditions of 1200 °C and 6 GPa. The synth...

Topochemical reactions between CaCrO3 and polyvinylidene difluoride yield the new fluorinated phase CaCrO2.5F0.5, which was characterized by powder synchrotron X-ray diffraction, X-ray photoemission spectroscopy, and magnetic susceptibility measurements. The reaction proceeds via reduced oxide intermediates, CaCrO2.67 and CaCrO2.5, in which CrO6 octahedral and CrO4 tetrahedral layers are stacked in a different manner along the c axis of CaCrO3. These two intermediate phases can be selectively synthesized by the carbothermal reduction with g-C3N4. Both CaCrO3 and CaCrO2.5F0.5 adopt the same orthorhombic space group, Pbnm; however, the fluorinated phase has decreased Cr-O-Cr bond angles as compared to the parent compound in both the ab plane and along the c-direction, which indicates an increased orthorhombic distortion due to the fluorination. While the oxygen vacancies are ordered in both intermediate phases, CaCrO2.67 and CaCrO2.5, a site preference for fluorine in the oxyfluoride phase cannot be confirmed. CaCrO3 and CaCrO2.5F0.5 undergo antiferromagnetic phase transitions involving spin canting, where the fluorination causes the transition temperature to increase from 90 K to 110 K, as a result of the competition between the increased octahedral tilting and the enhancement of superexchange interactions involving Cr3+ ions in the CaCrO2.5F0.5 structure.

Chalcogenide-containing compounds have been widely studied as infrared nonlinear optical (NLO) materials. However, they have never been applied in the ultraviolet (UV) region owing to the high energy levels of chalcogen anions, leading to band gap narrowing. We report the synthesis of a new UV NLO oxysulfide La

The metallic $\mathrm{LiOs}{\mathrm{O}}_{3}$ undergoes a transition to a polar phase below ${T}_{s}\ensuremath{\approx}140\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. This unusual property provides a unique opportunity to study the interaction between free electrons and electric dipoles. We report a suite of measurements of physical properties in $\mathrm{LiOs}{\mathrm{O}}_{3}$ as a function of temperature, including resistivity and magnetoresistance down to 0.16 K, thermoelectric power, high-precision magnetization, specific heat, and thermal conductivity on textured single-crystal samples. Enhancements from the electron contribution to the specific heat and the paramagnetic susceptibility indicate that electrons in $\mathrm{LiOs}{\mathrm{O}}_{3}$ are highly correlated. An anomalously large Kadowaki-Woods ratio also supports the argument of strongly correlated electrons in $\mathrm{LiOs}{\mathrm{O}}_{3}$. In the nonpolar phase above ${T}_{s}$, electrons are coupled strongly to the lattice vibrations, which leads to the resistivity saturation at high temperatures and eventually a crossover to the hopping conduction. The data of thermal conductivity and specific heat are consistent with an order-disorder transition at ${T}_{s}$. The analysis of critical behavior in the resistivity, specific heat, and the thermal conductivity provides useful information for understanding the electron-dipole interaction in $\mathrm{LiOs}{\mathrm{O}}_{3}$.

We report magnetic, transport, neutron diffraction, and muon spin rotation data showing that Pb$_2$CoOsO$_6$, a newly synthesized metallic double-perovskite with a centrosymmetric space group at room temperature, exhibits a continuous second-order phase transition at 45 K to a magnetically ordered state with a non-centrosymmetric space group. The absence of inversion symmetry is very uncommon in metals, particularly metallic oxides. In contrast to the recently reported ferroelectric-like structural transition in LiOsO$_3$, the phase transition in Pb$_2$CoOsO$_6$ is driven by a long-range collinear antiferromagnetic order, with propagation vector $\textbf{k} = (\frac{1}{2},0,\frac{1}{2})$, which relieves the frustration associated with the symmetry of themagnetic exchanges. This magnetically-driven loss of inversion symmetry represents a new frontier in the search for novel metallic behavior., 5 pages, 3 figures

Y2MnGa(Mn4–xGax)O12 solid solutions were synthesized at high pressure of ∼6 GPa and high temperature of ∼1570 K for the 0 ≤ x ≤ 3 compositional range. Synchrotron X-ray and neutron powder diffraction were used to study the crystal structures and cation distributions. These solutions adopt the parent structure of the A-site columnar-ordered quadruple perovskite family with space group P42/nmc (No. 137). They have lattice parameters of a = 7.36095 A and c = 7.753 84 A (x = 0), a = 7.361 68 A and c = 7.716 16 A (x = 1), a = 7.360 34 A and c = 7.67142 A (x = 2), and a = 7.363 93 A and c = 7.616 85 A (x = 3) at room temperature. The x = 0 sample has a cation distribution of [Y3+2]A[Mn3+]A′[Ga3+0.68Mn2+0.32]A″[Mn3.68Ga0.32]BO12 with a preferred localization of Ga3+ in the tetrahedral A″ site and with a small amount of Ga3+ in the octahedral B site. A complete triple A-site order, [Y3+2]A[Mn3+]A′[Ga3+]A″[Mn3+4–xGa3+x]BO12, is realized for x ≥ 1. All samples demonstrate spin-glass-like magnetic properties, and th...

A-site-ordered quadruple perovskite CeCu3Cr4O12 was prepared by a high-pressure, high-temperature method at 7.7 GPa and about 1670 K. Its crystal structure was investigated using synchrotron X-ray powder diffraction between 100 and 590 K. In this temperature range, it crystallizes in the parent cubic structure for A-site-ordered quadruple perovskites with space group Im-3. It exhibits a ferrimagnetic transition at TC = 333 K. Very small changes of Cu O and Cr O bond lengths were found at TC, and no changes in Ce O bond lengths. Ce O bond lengths of CeCu3Cr4O12 (about 2.525 A at 290 K) were very close to those of CeCu3Mn4O12 and CeCu3Fe4O12 suggesting the Ce4+ oxidation state and the charge distribution as Ce4+Cu2+3Cr3.5+4O12. No intersite charge transfer or charge disproportionation transitions were found in CeCu3Cr4O12.

High-pressure RMn3O6 manganites (belonging to a family of A-site columnar-ordered quadruple perovskites A2A′A″B4O12, where A′ is a site with a square-planar coordination and A″ is a site with a tetrahedral coordination) are prone to cation non-stoichiometry: they are rare-earth-deficient, R1−xMn3+xO6, for R = Ho, Y, Er, and Tm and manganese-deficient, R1+xMn3−xO6, for R = Gd. Here we investigated their crystal structures using single-crystal X-ray diffraction and synchrotron X-ray powder diffraction at room temperature. We found that the rare-earth deficiency is formed by doping of Mn2+ into the A site: [Er3+1.78Mn2+0.22]A[Mn3+]A′[Mn2+]A′′[Mn3+2]B1[Mn3.61+2]B2O12. The manganese deficiency is realized through doping of a small amount of Gd3+ into the A″ site: [Gd3+2]A[Mn3+]A′[Mn2+0.87Gd3+0.13]A′′[Mn3+2]B1[Mn3.44+2]B2O12. They all crystallize in space group Pmmn with layered charge ordering at the B sites. They are structurally related to CaFeTi2O6. Cation non-stoichiometry is supported by variations of the oxidation states of manganese at one of the B sites.

A new polymorph of the triple perovskite Ba3CuOs2O9, which usually exists in the orthorhombic phase, was synthesized under high-pressure and high-temperature conditions at 6 GPa and 1100 °C. Under the synthetic condition, Ba3CuOs2O9 crystallizes into a hexagonal structure (P63/mmc) with a = 5.75178(1) A and c = 14.1832(1) A, and undergoes a 1.36% increment in density, compared to that of the orthorhombic phase. Although Ba3CuOs2O9 maintains its 6 H perovskite-type structure, the distribution of Cu and Os atoms are dramatically altered; (Cu)4a(Os,Os)8f transits to (Os)2a(Cu,Os)4f ordering over the corner- and face-sharing sites, respectively. The hexagonal Ba3CuOs2O9 exhibits a ferrimagnetic transition at 290 K, which is in stark contrast to the antiferromagnetic transition at 47 K exhibited by the orthorhombic Ba3CuOs2O9. The enhanced transition temperature is most likely due to the strongly antiferromagnetic Os5+–O–Os5+ bonds and the moderately antiferromagnetic Os5+–O–Cu2+ bonds, the angles of which are both approximately 180°. The 290 K ferrimagnetic transition temperature is the highest reported for triple-perovskite osmium oxides. Besides, the coercive field is greater than 70 kOe at 5 K, which is remarkable among the coercive fields of magnetic oxides.

Sm2MnMn(Mn4–xTix)O12 with 1 ≤ x ≤ 3 were prepared by a high-pressure, high-temperature method at 6 GPa and about 1570–1670 K. They belong to a family of A-site columnar-ordered quadruple perovskite...

For high-critical-temperature (high-${T}_{\text{c}}$) superconductors, the normal state transport properties at low temperatures are of great importance to understand the Fermi surface structure and carrier profile. In this work we studied the doped ultrathin ${\mathrm{Ba}}_{0.57}{\mathrm{K}}_{0.43}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ system, a member of the optimally doped 122-type multigapped iron-based superconductors with complex superconducting gap structure. To explore the normal state resistivity below the zero-field superconducting ${T}_{\text{c}}$, both Co and Zn dopants were substituted into the superconducting ${\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ layer to suppress the superconductivity. The temperature dependence of in-plane resistivity below ${T}_{\text{c}}$ reveals a typical metallic behavior with the magnetic fields up to 45 T along $c$ axis. A linear dependence of Hall resistivity $({\ensuremath{\rho}}_{xy})$ is observed for ${\mathrm{Ba}}_{0.57}{\mathrm{K}}_{0.43}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ and ${\mathrm{Ba}}_{0.57}{\mathrm{K}}_{0.43}{({\mathrm{Fe}}_{0.96}{\mathrm{Zn}}_{0.04})}_{2}{\mathrm{As}}_{2}$ at high magnetic field, indicating a conventional metal profile. Nevertheless, the Co dopants lead to a decreasing $d{\ensuremath{\rho}}_{xy}/dH$ when the field is above 20 T. Such transformation of carrier transport properties may be contributed by band shift within a two-carrier model.

We have used muon spin rotation and relaxation (

We have used muon spin rotation and relaxation (μSR) and 23Na nuclear magnetic resonance (NMR) spectroscopic methods in the NaOsO3 antiferromagnetic phase to determine the temperature evolution of the magnetic order parameter and the role of the magnetic fluctuations at the Néel temperature. Additionally, we performed muon spin relaxation measurements in the vicinity of TA = 30 K, where the appearance of an anomaly in the electrical resistivity was suggested to be due to a progressive reduction of the Os magnetic moment associated with spin fluctuation. Our measurements suggest the absence of prominent change in the spin fluctuations frequency at TA, within the muon probing time scale and the absence of a reduction of the localized Os magnetic moment reflected by the stability within few permille of the local magnetic field strength sensed by the muons below 50 K.

We investigate the physical properties of the Shastry-Sutherland lattice material BaNd$_2$ZnO$_5$. Neutron diffraction, magnetic susceptibility, and specific heat measurements reveal antiferromagnetic order below 1.65 K. The magnetic order is found to be a 2-$\boldsymbol{Q}$ magnetic structure with the magnetic moments lying in the Shastry-Sutherland lattice planes comprising the tetragonal crystal structure of BaNd$_2$ZnO$_5$. The ordered moment for this structure is 1.9(1) $\mu_B$ per Nd ion. Inelastic neutron scattering measurements reveal that the crystal field ground state doublet is well separated from the first excited state at 8 meV. The crystal field Hamiltonian is determined through simultaneous refinement of models with both the LS coupling and intermediate coupling approximations to the inelastic neutron scattering and magnetic susceptibility data. The ground state doublet indicates that the magnetic moments lie primarily in the basal plane with magnitude consistent with the size of the determined ordered moment., Comment: 13 pages, 8 figures

Powder neutron-diffraction experiments have been employed to establish the effects of site-selective magnetic dilution in the ${\mathrm{Sm}}_{2}{\mathrm{MnMnMn}}_{4\ensuremath{-}x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{12} A$-site columnar ordered quadruple perovskite manganites ($x=1, x=2$, and $x=3$). We show that in all three compositions the Mn ions adopt a collinear ferrimagnetic structure below 27, 62, and 34 K, respectively. An unexpected increase in the ordering temperature was observed between the $x=1$ and $x=2$ samples, which indicates a considerable departure from mean-field behavior. This result is corroborated by large reductions in the theoretical ground-state magnetic moments observed across the series, which indicate the presence of spin fluctuations and/or disorder. We show that long-range magnetic order in the $x=3$ sample, which occurs below the percolation threshold for B-B exchange, can only be understood to arise if it is mediated via both A-B and B-B exchange, hence confirming the importance of A-B exchange interactions in these materials. Finally, we show that site-selective magnetic dilution enables the tuning of a ferrimagnetic compensation point and the introduction of temperature-induced magnetization reversal.

A new ternary chromium disulfide, Ba9Cr4S19, has been grown out of BaCWl(2) molten salt. Single-crystal structure analysis revealed that it crystallizes in the centrosymmetric space group C2/c with lattice parameters: a = 12.795(3) angstrom, b = 11.3269(2) angstrom, c = 23.2057(6) angstrom, beta = 104.041(3)degrees, and Z = 4. Ba9Cr4S19 comprises four face-sharing Cr-centered octahedra with disulfide ions occupying sites on each terminal face. The resulting Cr4S15 tetramer units are isolated by nonmagnetic Ba-centered polyhedra in the ab plane and barium disulfide (=Ba-4(S-2)(2)) layers along the c-axis. Following the structure analysis, the title compound should be expressed as [Ba2+](9)[Cr3+](4)[(S-2)(2-)](4)[S2-](11), which is also consistent with Cr2p X-ray photoemission spectra showing trivalent states of the Cr atoms. The unique Cr-based zero-dimensional structure with the formation of these disulfide ions can be achieved for the first time in ternary chromium sulfides, which adopt 1-3 dimensional frameworks of Cr-centered polyhedra.

A high-pressure synthesis method was employed to prepare Mn-self-doped perovskites (

The double perovskite oxide ${\mathrm{Sr}}_{2}\mathrm{CrOs}{\mathrm{O}}_{6}$ with a $3{d}^{3}\text{\ensuremath{-}}5{d}^{3}$ configuration exhibits very high-${T}_{C}$ ferrimagnetism (\ensuremath{\sim}725 K) at the end point of half-metallicity. Many substitution studies have been conducted theoretically and experimentally over the last two decades to shed more light on the open issue of how the $3{d}^{3}\text{\ensuremath{-}}5{d}^{3}$ configuration generates the high-${T}_{C}$ ferrimagnetic state and to accelerate development toward applications. We have succeeded in synthesizing a solid solution of ${\mathrm{Sr}}_{2}{\mathrm{Cr}}_{1--x}{\mathrm{Ni}}_{x}\mathrm{Os}{\mathrm{O}}_{6}$ under high-pressure and high-temperature conditions. ${\mathrm{Sr}}_{2}{\mathrm{Cr}}_{0.5}{\mathrm{Ni}}_{0.5}\mathrm{Os}{\mathrm{O}}_{6}$ exhibits magnetization sixfold greater ($\ensuremath{\sim}1.2\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$/formula unit at 5 K) than that of ${\mathrm{Sr}}_{2}\mathrm{CrOs}{\mathrm{O}}_{6}$. This enhancement is preserved even at room temperature. X-ray absorption spectroscopy revealed that the electronic configuration is ${\mathrm{Sr}}_{2}{({{\mathrm{Cr}}^{3+}}_{2/3}{{\mathrm{Cr}}^{6+}}_{1/3})}_{0.5}{{\mathrm{Ni}}^{2+}}_{0.5}{\mathrm{Os}}^{5+}{\mathrm{O}}_{6}$, indicating that the valence state of Os does not change from the host state $[{\mathrm{Os}}^{5+}(5{d}^{3})]$. Instead, nonmagnetic ${\mathrm{Cr}}^{6+}(3{d}^{0})$ is partly generated among coexisting ${\mathrm{Cr}}^{3+}(3{d}^{3})$. X-ray magnetic circular dichroism measurements showed that the Os ions are antiferromagnetically coupled to the Cr and ferromagnetically to the Ni. The replacement of antiferromagnetic Cr by ferromagnetic Ni explains the increase of the net magnetism in this ferrimagnetic system. We infer that the strong antiferromagnetic exchange interaction of the $3{d}^{3}\text{\ensuremath{-}}5{d}^{3}$ configuration associated with the ${\mathrm{Cr}}^{3+}\text{\ensuremath{-}}\mathrm{O}\text{\ensuremath{-}}{\mathrm{Os}}^{5+}$ bond still accounts for the robust high-${T}_{C}$ ferrimagnetism of the Ni-substituted series. We deduce from the experiments that the ferromagnetic exchange interaction of the $3{d}^{8}\text{\ensuremath{-}}5{d}^{3}$ configuration of the ${\mathrm{Ni}}^{2+}\text{\ensuremath{-}}\mathrm{O}\text{\ensuremath{-}}{\mathrm{Os}}^{5+}$ is stronger than that of the $3{d}^{8}\text{\ensuremath{-}}3{d}^{3}$ configuration of the ${\mathrm{Ni}}^{2+}\text{\ensuremath{-}}\mathrm{O}\text{\ensuremath{-}}{\mathrm{Cr}}^{3+}$, suggesting that the larger 5d orbital of the Os allows for a stronger virtual hopping from the Ni than the smaller $3d$ orbital of the Cr. The present results can help to further develop practical materials and to resolve open issues concerning the relative strengths of the various exchange interactions.