NaV2O4: a Quasi-1D Metallic Antiferromagnet with Half-Metallic Chains

NaV2O4 crystals were grown under high pressure using a NaCl flux, and the crystals were characterized with X-ray diffraction, electrical resistivity, heat capacity, and magnetization. The structure of NaV2O4 consists of double chains of edge-sharing VO6 octahedra. The resistivity is highly anisotropic, with the resistivity perpendicular to the chains more than 20 times greater than that parallel to the chains. Magnetically, the intrachain interactions are ferromagnetic and the interchain interactions are antiferromagnetic; 3D antiferromagnetic order is established at 140 K. First principles electronic structure calculations indicate that the chains are half metallic. Interestingly, the case of NaV2O4 seems to be a quasi-1D analogue of what was found for half-metallic materials.Comment: 14 pages, including 4 figures and 1 table, accepted for publication in PR

Methyl 2,2-bis­(2,4-dinitro­phen­yl)ethano­ate

In the title compound, C15H10N4O10, the dihedral angle between the aromatic rings is 89.05 (16)°. One O atom of one of the nitro groups is disordered over two sites in a 0.70:0.30 ratio. In the crystal, the mol­ecules are linked by weak C—H⋯O inter­actions

2-Phenyl­acetic acid–(E,E)-4,4’-(hydra­zinediylidene)dipyridine (2/1)

The asymmetric unit of the title co-crystal, C12H10N4·2C8H8O2, comprises a single mol­ecule of 2-phenyl­acetic acid and half a mol­ecule of 4-pyridine­aldazine as this is situated about a centre of inversion. Mol­ecules are connected into a three component aggregate via O—H⋯N hydrogen bonds. As the carb­oxy­lic acid group is almost normal to the plane through the benzene ring to which it is attached [C—C—C—C = 93.7 (3) °], and the 4-pyridine­aldazine mol­ecule is planar (r.m.s. deviation of the 16 non-H atoms = 0.010 Å), the overall shape of the aggregate is that of an extended chair. In the crystal packing, layers of three component aggregates stack along the c axis

catena-Poly[[[(2-pyridone-κO)silver(I)]-μ-2-pyridone-κ2 O:O] hexa­fluorido­phosphate]

The asymmetric unit of the polymeric title salt, {[Ag(C5H5NO)2]PF6}n, comprises an AgI cation (located on a twofold axis), two 2-pyridone ligands (with distinct coordination modes), and half a PF6 − anion (situated on a centre of inversion). The AgI atom is in an approximately octa­hedral AgO6 coordination geometry, which is stabilized by intra­molecular N—H⋯O hydrogen bonds. The result of the bridging mode of the 2-pyridone ligand is the formation of a supra­molecular chain along the c axis; these are consolidated in the crystal by C—H⋯F inter­actions

Single crystal of superconducting SmFeAsO1-xFy grown at high pressure

Single crystals of SmFeAsO1-xFy of a size up to 120 micrometers have been grown from NaCl/KCl flux at a pressure of 30 kbar and temperature of 1350-1450 C using the cubic anvil high-pressure technique. The superconducting transition temperature of the obtained single crystals varies between 45 and 53 K.Obtained crystals are characterized by a full diamagnetic response in low magnetic fields and by a high critical current density in high magnetic fields. Structural refinement has been performed on single crystal. Differential thermal analysis investigations at 1 bar Ar pressure show decomposition of SmFeAsO1-xFy at 1302 C.Comment: 12 pages, 3 tables, 6 figure

Interplay of composition, structure, magnetism, and superconductivity in SmFeAs1-xPxO1-y

Polycrystalline samples and single crystals of SmFeAs1-xPxO1-y were synthesized and grown employing different synthesis methods and annealing conditions. Depending on the phosphorus and oxygen content, the samples are either magnetic or superconducting. In the fully oxygenated compounds the main impact of phosphorus substitution is to suppress the N\'eel temperature TN of the spin density wave (SDW) state, and to strongly reduce the local magnetic field in the SDW state, as deduced from muon spin rotation measurements. On the other hand the superconducting state is observed in the oxygen deficient samples only after heat treatment under high pressure. Oxygen deficiency as a result of synthesis at high pressure brings the Sm-O layer closer to the superconducting As/P-Fe-As/P block and provides additional electron transfer. Interestingly, the structural modifications in response to this variation of the electron count are significantly different when phosphorus is partly substituting arsenic. Point contact spectra are well described with two superconducting gaps. Magnetic and resistance measurements on single crystals indicate an in-plane magnetic penetration depth of 200 nm and an anisotropy of the upper critical field slope of 4-5. PACS number(s): 74.70.Xa, 74.62.Bf, 74.25.-q, 81.20.-nComment: 36 pages, 13 figures, 2 table

Non-Fermi liquid behavior in a fluctuating valence system, the filled skutterudite compound CeRu_{4}As_{12}

Electrical resistivity $\rho$, specific heat C, and magnetic susceptibility $\chi$ measurements made on the filled skutterudite CeRu_4As_{12} reveal non-Fermi liquid (NFL) T - dependences at low T, i.e., $\rho$(T) $\sim$ T^{1.4} and weak power law or logarithmic divergences in C(T)/T and $\chi$(T). Measurements also show that the T - dependence of the thermoelectric power S(T) deviates from that seen in other Ce systems. The NFL behavior appears to be associated with fluctuations of the Ce valence between 3^+ and 4^+ rather than a typical Kondo lattice scenario that would be appropriate for an integral Ce valence of 3^+.Comment: 18 pages, 5 figure

2-Amino­benzoic acid–4-(pyridin-4-yl­disulfan­yl)pyridine (1/1)

The title 1:1 co-crystal, C7H7NO2·C10H8N2S2, features a highly twisted 4-(pyridin-4-yldisulfan­yl)pyridine mol­ecule [dihedral angle between the pyridine rings = 89.06 (10)°]. A small twist is evident in the 2-amino­benzoic acid mol­ecule, with the C—C—C—O torsion angle being −7.7 (3)°. An N—H⋯O hydrogen bond occurs in the 2-amino­benzoic acid mol­ecule. In the crystal, mol­ecules are linked by O—H⋯N and N—H⋯N hydrogen bonds into a supra­molecular chain along the b axis. These are connected into layers by π–π inter­actions occurring between pyridine rings [centroid–centroid distance = 3.8489 (15) Å]. The layers are connected along the a axis by C—H⋯O contacts. The crystal studied was a racemic twin

Poly[(μ2-2,2′-bipyridine-κ2 N:N′)bis­(μ3-2,2,2-trifluoro­acetato-κ3 O:O:O′)disilver(I)]

In the title salt, [Ag2(CF3CO2)2(C10H8N2)]n, which may also be regarded as a coordination polymer if long Ag⋯O inter­actions are considered, each of the N atoms of the somewhat twisted 2,2′-bipyridine mol­ecule [N—C—C—N = −27.5 (4)°] binds to an Ag atom, and each of the carboxyl­ate ligands is tridentate, linking to three Ag atoms. The bidentate carboxyl­ate O atoms bridge the same two Ag atoms, resulting in the formation of Ag2O2 rings. These rings are bridged by the 2,2′-bipyridine ligands, forming a chain along the b axis. The chains are linked into double chains via the remaining Ag—O bonds and Ag⋯Ag contacts. As a consequence of the Ag⋯Ag contacts, the NO4 donor set about each Ag atom is heavily distorted. Finally, the chains are linked into a three-dimensional network by a combination of C—H⋯O and C—H⋯F inter­actions

Aqua­(trifluoro­methane­sulfonato)­bis­(1,3,7-trimethyl­purine-2,6-dione)silver(I)

In the title compound, [Ag(CF3SO3)(C8H10N4O2)2(H2O)], the AgI atom is coordinated by two caffeine N atoms and, at longer distances, two O atoms of a coordinated water mol­ecule and the trifluoro­methane­sulfonate anion, resulting in an AgN2O2 seesaw geometry. The caffeine mol­ecules are roughly coplanar [dihedral angle = 5.81 (5)°]. In the crystal, mol­ecules self-assemble into a linear supra­molecular chain along the c axis via O—H⋯O hydrogen bonds involving the coordinated water moledcule and carbonyl O atoms. The packing is consolidated by weak C—H⋯O inter­actions