Sr2CoWO6 perovskite has been prepared in polycrystalline form by solid-state reaction at 1150 °C. This material has been studied by high-resolution synchrotron X-ray and neutron powder diffraction (NPD), magnetic measurements, and differential scanning calorimetry (DSC). At room temperature, the crystal structure is tetragonal, space group I4/m, with a = 5.58277(1) Å and c = 7.97740(1) Å. The structure contains alternating CoO6 and WO6 octahedra, tilted in anti-phase by 7.24° in the basal ab plane along the [001] direction of the pseudocubic cell. This corresponds to the a 0 a 0 c - Glazer's notation as derived by Woodward for 1:1 ordering of double perovskites, consistent with space group I4/m. DSC and NPD measurements as a function of temperature indicate a structural transition from tetragonal to monoclinic (space group P21/n) at 260 K. At 2 K the cell parameters are a = 5.61267(8) Å, b = 5.58753(8) Å, c = 7.8994(1) Å, and β = 90.041(3)°. The structure contains alternating CoO6 and WO6 octahedra, tilted in-phase by 4.77° along the [001] direction of the pseudocubic cell and in anti-phase by 5.82° along the [010] and [100] directions. This corresponds to the a - a - c + Glazer's notation as derived by Woodward for 1:1 ordering in double perovskites, consistent with space group P21/n. Magnetic and neutron diffraction measurements indicate an antiferromagnetic ordering below T N = 24 K. The magnetic moment calculated through the linear fit of the Curie−Weiss law at high temperatures (5.20 μB) indicates that the orbital contribution is unquenched at high temperatures, which is consistent with high-spin Co2+ (4T1g ground state) in a quasi-regular octahedral environment. As prepared, the sample is an electrical insulator. Magnetic and electrical properties and bond valence sums are consistent with the electronic configuration Co2+(3d7)−W6+(5d0).

Raman scattering is used to investigate the room temperature phonons of tetragonal (I4∕m) Sr2CoWO6 and monoclinic (P21∕n) Ca2CoWO6, Sr2CoTeO6, and Ca2CoTeO6 double perovskites. Both tetragonal and monoclinic structures result from small distortions of the Fm3¯m cubic lattice. Therefore, phonons were assigned according to correlations with those observed in the prototype A2B′B″O6 Fm3¯m cubic structure and the internal vibrational modes of the oxygen octahedra. The observed shifts of some vibrations in the A2CoBO6 compounds upon changing either A or B elements are tentatively explained.

Sr2CoMoO6 perovskite has been prepared in polycrystalline form by thermal treatment, in air, of previously decomposed citrate precursors. This material has been studied by X-ray (XRD) and neutron powder diffraction (NPD), thermal analysis, and magnetic, magnetotransport, and Hall effect measurements. At room temperature, the crystal structure is tetragonal with a space group I4/m, with a = 5.565 03(5) and c = 7.948 10(8) Å. The crystal contains alternating CoO6 and MoO6 octahedra, tilted by 6.8° in the basal ab plane. Magnetic measurements indicate an antiferromagnetic ordering below T N = 37 K. As prepared, the sample is an electrical insulator. The topotactic reduction of the stoichiometric sample, in H2/N2 flows, leads to oxygen-deficient double perovskites, Sr2CoMoO6 - δ, δ = 0.03 and 0.14. The magnetic behavior of the reduced samples suggests the presence of ferromagnetic domains characterized by Curie temperatures of T C = 350−370 K. The conductivity dramatically increases upon H2 reduction; the number of charge carriers, as determined by Hall effect measurements, are 1.7 × 10-7 and 6 × 10-6 electrons per unit cell for δ = 0.03 and 0.14 samples, respectively. Moreover, the reduced samples exhibit colossal magnetoresistance, as high as 30% at 12 K for H = 9T. Magnetic and magnetotransport results are consistent with a large component of itinerancy for down-spin Mo t2g electrons, injected through hydrogen reduction.

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double perovskites have been prepared in polycrystalline form by solid state reaction, in air. These materials have been studied by X-ray diffraction (XRD), neutron powder diffraction (NPD) and magnetic measurements. At room temperature, the crystal structure of Sr 3 Fe 2 TeO 9 is tetragonal, space group I4/m, with a = b = 5.55902(4) A ˚, c = 7.885(1) A ˚, whereas Ba 3 Fe 2 TeO 9 presents a hexagonal lattice, space group P6 3 /mmc, with a = 5.7670(1) A ˚, c = 14.1998(4) A ˚. The structure of Sr 3 Fe 2 TeO 9 , which can ideally be rewritten as Sr 2 Fe(Fe 1/3 Te 2/3 )O 6 , can be described as the result of a single anti-phase tilting of the FeO 6 and (Fe,Te)O 6 octahedra along the c axis, exhibiting a tilting angle of 4.5u at RT. Ba 3 Fe 2 TeO 9 shows a different stacking of the Fe/Te octahedra: the structure is constituted by dimer units of (Fe,Te)O 6 octahedra sharing a face along the c axis; the dimers are connected, sharing corners, by a single layer of FeO 6 octahedra. In both Sr and Ba compounds a certain degree of antisite disordering has been detected, implying the presence of about 15% Te at Fe positions. Magnetic measurements show the onset of ferrimagnetic ordering at relatively high temperatures of 717 and 711 K for the Sr and Ba compounds, respectively; however the magnetization isotherms at 2 K exhibit, for H = 50 kOe, maximum magnetization values close to 0.8 m B f.u. 21 and 0.35 m B f.u. 21 for Sr and Ba compounds respectively, although full saturation is not reached. The extremely weak magnetic scattering contribution observed on the low-temperature NPD patterns for Sr 3 Fe 2 TeO 9 is in contrast with the well-established ferrimagnetic structures observed for other members of the Sr 3 Fe 2 B0O 9 double perovskite series (B0 = U, Mo, W). This distinct behavior is discussed as a function of the chemical nature of the different B0 hexavalent cations.

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Background. The production of anti-drug antibodies (ADAs) against IgG monoclonal antibodies (mAbs) targeting tumour necrosis factor (TNF) is an important cause of loss of response to anti-TNF mAbs in patients with inflammatory bowel diseases (IBD) such as Crohn's disease (CD) and ulcerative colitis (UC). Since receptors for the Fc portion of IgG (FCGRs) are involved in the degradation of IgG complexes, we hypothesised that a polymorphism in FCGR3A (V158F; rs396991) gene could be involved in anti-TNF ADA generation and treatment resistance. Material and Methods. A cohort of 103 IBD patients (80 CD, 23 UC) were genotyped and serum level of both anti-TNFs (infliximab or adalimumab) and ADA against them were measured. Results. No significant differences were observed between ADA occurrence or V158F genotype and type of disease or the kind of anti-TNF administrated. Interestingly, VV genotype correlated with patients producing ADA (VV: 37.5% vs. FV: 10.6% or FF: 5%; p=0.004) and was an independent predictor of this event after multivariate analysis. Moreover, VV genotype also correlated with those patients receiving anti-TNF dose intensification (p=0.03). Conclusion. FCGR3A V158F polymorphism seems to be associated with ADA production against mAbs and it could be taken into account when considering the dose and type of anti-TNF in IBD patients.

The synthesis, crystal structure, and dielectric properties of the novel double perovskite Pb(2)TmSbO(6) are described. The room-temperature crystal structure was determined by ab initio procedures from neutron powder diffraction (NPD) and synchrotron X-ray powder diffraction (SXRPD) data in the monoclinic C2/c (No. 15) space group. This double perovskite contains a completely ordered array of alternating TmO(6) and SbO(6) octahedra sharing corners, tilted in antiphase along the three pseudocubic axes, with an a(-)b(-)b(-) tilting scheme, which is very unusual in the crystallochemistry of perovskites. The lead atoms occupy a highly asymmetric void with 8-fold coordination due to the stereoactivity of the Pb(2+) lone electron pair. This compound presents three successive phase transitions in a narrow temperature range (at T1 = 385 K, T2 = 444 K, and T3 = 460 K in the heating run) as shown by differential scanning calorimetry (DSC) data. The crystal structure and temperature-dependent NPD follow the space-group sequence C2/c → P2(1)/n → R3 → Fm3m. This is a novel polymorph succession in the high-temperature evolution of perovskite-type oxides. The Tm/Sb long-range ordering is preserved across the consecutive phase transitions. Dielectric permittivity measurements indicate the presence of a paraelectric/antiferroelectric transition (associated with the last structural transition), as suggested by the negative Curie temperature obtained from the Curie-Weiss fit of the reciprocal permittivity.