Tripraseodymium penta­iron(III) dodeca­oxide, Pr3Fe5O12: a synchrotron radiation study

The title compound, penta­iron tripraseodymium dodeca­oxide (PrIG), has an iron garnet structure. There are two Fe site symmetries. One of the Fe atoms is coordinated by six O atoms, forming a slightly distorted octa­hedron, and has site symmetry. The other Fe atom is coordinated by four O atoms, forming a slightly distorted tetra­hedron, and has site symmetry. FeO6 octa­hedra and FeO4 tetra­hedra are linked together by corners. The Pr atom is coordinated by eight O atoms, forming a distorted dodeca­hedron, and has 222 site symmetry. The O atoms occupy the general positions

Trineodymium(III) penta­iron(III) dodeca­oxide, Nd3Fe5O12

The title compound, Nd3Fe5O12 (NdIG), has an iron garnet structure. One of the Fe atoms is coordinated by six O atoms in a slightly distorted octa­hedral geometry and has site symmetry. The other Fe atom is coordinated by four O atoms in a slightly distorted tetra­hedral geometry and has site symmetry. The FeO6 octa­hedron and FeO4 tetra­hedron are linked together by corners. The Nd atom is coordinated by eight O atoms in a distorted dodeca­hedral geometry and has 222 site symmetry. The O atoms occupy general positions

Filled skutterudite structure of europium ruthenium polyphosphide, EuRu4P12

The crystal structure of EuRu4P12 is isotypic with filled skutterudite structures of rare earth transition metal poly­phosphides: RFe4P12 (R = Ce, Pr, Nd, Sm and Eu), RRu4P12 (R = La, Ce, Pr and Nd) and ROs4P12 (R = La, Ce, Pr and Nd). The Ru cation is coordinated by six P anions in a distorted octa­hedral manner. The partially occupied Eu position (site occupancy 0.97) is enclosed by a cage formed by the corner-shared framework of the eight RuP6 octa­hedra

Apatite-type SrPr4(SiO4)3O

Single crystals of the title compound, strontium tetra­praseo­dymium tris­(silicate) oxide, SrPr4(SiO4)3O, have been grown by the self-flux method using SrCl2. The structure is isotypic with the apatite supergroup family having the generic formula IX M12 VII M23(IV TO4)3 X, where M = alkaline earth and rare earth metals, T = Si and X = O. The M1 site (3.. symmetry) is occupied by Pr and Sr atoms with almost even proportions and is surrounded by nine O atoms forming a tricapped trigonal prism. The M2 site (m.. symmetry) is almost exclusively occupied by Pr and surrounded by seven O atoms, forming a distorted penta­gonal bipyramid. The Si atom (m.. symmetry) is surrounded by two O (m.. symmetry) and two O atoms in general positions, forming an isolated SiO4 tetra­hedron. Another O atom at the inversion centre (.. symmetry) is surrounded by three M2 sites, forming an equilateral triangle perpendicular to the c axis

(CaxNd11-x)Ru4O24 (x = 4.175)

Single crystals of the title compound, calcium neodymium ruthenate, (CaxNd11-x)Ru4O24 (x = 4.175), have been grown by the flux method. The structure consists of two crystallographically independent RuO6 octa­hedra, which are isolated from each other and embedded in a matrix composed of the Ca and Nd atoms. There are seven M sites which accommodate the Ca and Nd atoms with different populations. Four M sites at general positions are enriched with Nd, whereas the remaining three M sites on twofold rotation axes are enriched with Ca. The coordination numbers of O atoms to the M sites range from 6 to 9. The mean oxidation state of Ru was estimated at +4.79 from the composition analysis. The title compound is non-centrosymmetric and potentially multiferroic

Quantum critical behavior of the hyperkagome magnet Mn3CoSi

β-Mn-type family alloys Mn3TX (T = Co, Rh, and Ir; X = Si and Ge) have a three-dimensional antiferromagnetic (AF) corner-shared triangular network, i.e., the hyperkagome lattice. The antiferromagnet Mn3RhSi shows magnetic short-range order over a wide temperature range of approximately 500 K above the Néel temperature TN of 190 K. In this family of compounds, as the lattice parameter decreases, the long-range magnetic ordering temperature decreases. Mn3CoSi has the smallest lattice parameter and the lowest TN in the family. The quantum critical point (QCP) from AF to the quantum paramagnetic state is expected near a cubic lattice parameter of 6.15 Å. Although the Néel temperature of Mn3CoSi is only 140 K, the emergence of the quantum critical behavior in Mn3CoSi is discussed. We study how the magnetic short-range order appears in Mn3CoSi by using neutron scattering, μSR, and bulk characterization such as specific heat capacity. According to the results, the neutron scattering intensity of the magnetic short-range order in Mn3CoSi does not change much at low temperatures from that of Mn3RhSi, although the μSR short-range order temperature of Mn3CoSi is largely suppressed to 240 K from that of Mn3RhSi. Correspondingly, the volume fraction of the magnetic short-range order regions, as shown by the initial asymmetry drop ratio of μSR above TN, also becomes small. Instead, the electronic-specific heat coefficient γ of Mn3CoSi is the largest in this Mn3T Si system, possibly due to the low-energy spin fluctuation near the quantum critical point

Redetermination of Nd2Ti2O7: a non-centrosymmetric structure with perovskite-type slabs

Single crystals of dineodymium(III) dititanium(IV) heptaoxide, Nd2Ti2O7, were synthesized by the flux method and found to belong to the family of compounds with perovskite-type structural motifs. The asymmetric unit contains four Nd, four Ti and 14 O-atom sites. The perovskite-type slabs are stacked parallel to (010) with a thickness corresponding to four corner-sharing TiO6 octahedra. The Nd and Ti ions are displaced from the geometrical centres of respective coordination polyhedra so that the net polarization occurs along the c axis. The investigated crystals were all twinned and have a halved monoclinic unit cell in comparison with the first structure determination of this compound [Scheunemann & Müller-Buschbaum (1975). J. Inorg. Nucl. Chem. 37, 2261–2263]