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A high-pressure-synthesized double perovskite Sr2YOsO6 was investigated by synchrotron X-ray diffraction and measurements of its magnetic susceptibility, specific heat capacity, complex impedance, and complex dielectric constant. It crystallized into a monoclinic double perovskite structure (P21/n) with complete ordering of the Y and Os atoms. Its magnetic behaviors, including the antiferromagnetic transition temperature (∼52 K), Curie-Weiss effective moment [3.48(5) μB/Os], and Weiss temperature [−350.1(7) K], were close to the respective values of Sr2YOsO6 previously synthesized without an applied pressure of 6 GPa. Transport property measurements revealed that the lower limit of the activation energy was 192(1) meV and the charge gap remained open regardless of the presence of magnetic order, conflicting with the electron delocalization predicted by theoretical calculations. Further consideration, including theoretical and experimental investigations of the roles of spin–orbit coupling and U of the 5d ...

We investigated the upper critical fields of Ca10(Pt4As8)(Fe2–xPtxAs2)5 superconducting whiskers. The whiskers consist of several wire-like grains with diameter of around 200 nm, joined by grain boundaries whose misorientation angles are less than 5∘. The upper critical fields along c-axis and in ab-plane were observed as 49 T at 12 K and 50 T at 22 K, respectively, which can be extrapolated to ∼81 and ∼133 T at 0 K. The whisker demonstrated weak anisotropic factor and almost constant value of ∼2 below 15 K. The impressive transport properties of the whisker may find applications in fields like superconducting micro- and meso-structure systems.

Substitution of Sb with Sn was achieved in ferrimagnetic antiperovskite Mn3SbN. The experimental results indicate that with an increase in Sn concentration, the magnetization continuously decreases and the crystal structure of Mn3Sb1-xSnxN changes from tetragonal to cubic phase at around x of 0.8. In the doping series, step-like anomaly in the isothermal magnetization was found and this behavior was highlighted at x = 0.4. The anomaly could be attributed to the magnetic frustration, resulting from competition between the multiple spin configurations in the antiperovskite lattice. Meantime, Hc of 18 kOe was observed at x = 0.3, which is probably the highest among those of manganese antiperovskite materials reported so far. With increasing Sn content, the abrupt change of resistivity and the sharp peak of heat capacity in Mn3SbN were gradually weakened. The crystal structure refinements indicate the weakened change at the magnetic transition is close related to the change of c/a ratio variation from tetrago...

We investigated the critical current density (Jc) of Ba0.5K0.5Fe2As2 single-crystalline microbridges with thicknesses ranging from 276 to 18 nm. The Jc of the microbridge with thickness down to 91 nm is 10.8 MA/cm2 at 35 K, and reaches 944.4 MA/cm2 by extrapolating Jc(T) to T = 0 K using a two-gap s-wave Ginzburg-Landau model, well in accordance with the depairing current limit. The temperature, magnetic field, and angular-dependence of Jc(T,H,θ) indicated weaker field dependence and weakly anisotropic factor of 1.15 (1 T) and 1.26 (5 T), which also yielded the validity of the anisotropic Ginzburg-Landau scaling.

A resistive-switching phenomenon driven by antiferromagnetic phase separation is observed for a manganese nitride Mn3ZnN, which crystallizes in the antiperovskite structure. Measurements of the lattice parameters, magnetic susceptibility, electrical resistivity, and specific heat from 2 K to 300 K reveal antiferromagnetic phase separation that appears below a temperature of approximately 190 K. The mechanism of the phase separation is highly complicated; nevertheless the accompanying resistive-switching phenomenon is useful for non-volatile memory applications.

The crystal structure and the electronic and thermal properties of a high-quality polycrystalline TbFeAsO0.85 sample made by a high-pressure technique are investigated. The crystal structure, as determined by synchrotron X-ray powder diffraction, possesses a tetragonal unit cell (space group: P4/nmm) with lattice parameters of a=b=3.8851 A and c=8.3630 A. In order to elucidate the electronic structure and oxidation states of corresponding elements, X-ray absorption near-edge structure (XANES) spectra are presented. The XANES spectra confirm that the oxidation states of Fe, As, and Tb in the TbFeAsO0.85 sample are ∼Fe2+, ∼As3−, and ∼Tb3+, respectively, which are consistent with the previously reported band structure calculations. The n-type character of the charge carriers as revealed from XANES spectra is corroborated by the negative sign of the Seebeck coefficient (S) in the present study. The heat capacity (CP) measurement shows an anomaly in the vicinity of the superconducting transition temperature (T...

We report synthesis, structure, electrical transport and heat capacity of SmFeAsO. The title compound is synthesized by one-step encapsulation of stoichiometric FeAs, Sm, and Sm2O3 in an evacuated (10-5 Torr) quartz tube by prolong (72 hours) annealing at 1100oC. The as synthesized compound is crystallized in tetragonal structure with P4/nmm space group having lattice parameters a = 3.93726(33) A and c = 8.49802(07) A. The resistance (R-T) measurements on the compound exhibited ground state spin-density-wave (SDW)-like metallic steps below 140 K. Heat capacity CP(T) measurements on the title compound, showed an anomaly at around 140 K, which is reminiscent of the SDW ordering of the compound. At lower temperatures the CP(T) shows a clear peak at around 4.5 K. At lower temperature below 20 K, Cp(T) is also measured under an applied field of 7 Tesla. It is concluded that the CP(T) peak at 4.5 K is due to the anti-ferromagnetic(AFM) ordering of Sm3+ spins. These results are in confirmation with ordering of Sm in Sm2-xCexCuO4., 9 pages Text + Figs Contact Author (awana@mail.nplindia.ernet.in)

The perovskite Sr1−xHoxCoO3−δ shows room temperature ferromagnetism (Tc∼335K) in a severely limited composition range 0.2⩽x⩽0.25. The formal Co valence is almost constant at +3 regardless of the Ho concentration (x⩾0.2); thus, the high-spin state or the intermediate spin state of 3d6 Co should be mainly responsible for the magnetism. The ferromagnetism was found to accompany the formation of a superstructure 2ap×2ap×4ap (ap denotes a cubic perovskite cell). Besides, an additional superstructure 4(2ap)×4(2ap)×(4ap) was found at x=0.225, where the ferromagnetic volume in magnetic susceptibility was largest. The data suggest that the formation of the multiple superstructures probably plays a key role to establish the peculiar ferromagnetism.

We report on the thermoelectric properties of n-type homologous boron cluster compounds REB17CN and REB22C2N (RE=rare earth) in the temperature range of 300–1000 K. Boron cluster compounds like boron carbide have predominantly exhibited p-type behavior. REB17CN and REB22C2N exhibit n-type behavior without doping and are possible counterparts to boron carbide, which is known to be an exemplar p-type high temperature thermoelectric compound. With the hot press method it was only possible to prepare samples with low density and extremely low power factors. Two methods for improving the properties were investigated: spark plasma sintering of HoB17CN and YB22C2N and seeding of ErB17CN and ErB22C2N samples with metal borides like ErB4 and ErB6. Although absolute values of the power factor are still low, both methods are shown to yield routes for large increases of the power factor (a factor of 31 to 106 times for the samples measured) compared to conventional hot pressed samples.