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Single crystals of alkali aluminoboracites, A4B4Al3O12Cl (A = Li, Na), were grown using the self-flux method, and their isotypic cubic crystal structures were determined by single-crystal X-ray diffraction. Na4B4Al3O12Cl is the first reported sodium boracite, and its lattice parameter [13.5904 (1) Å] is the largest among the boracites consisting of a cation–oxygen framework reported so far. For both crystals, structure models refined in the cubic space group F\overline{4}3c, which assume that all cubic octant subcells in the unit cell are equivalent, converged with R1 factors of ∼0.03. However, the presence of weak hhl reflections with odd h and l values indicates that refinements in the space group F23, which presume a checkerboard-like ordering of two types of subcells with slightly different atomic positions, are more appropriate.

Single crystals of alkali aluminoboracites, A4B4Al3O12Cl (A = Li, Na), were grown using the self-flux method, and their isotypic cubic crystal structures were determined by single-crystal X-ray diffraction. Na4B4Al3O12Cl is the first reported sodium boracite, and its lattice parameter [13.5904 (1) A ° ] is the largest among the boracites consisting of a cation-oxygen framework reported so far. For both crystals, structure models refined in the cubic space group F43c, which assume that all cubic octant subcells in the unit cell are equivalent, converged with R1 factors of ~0.03. However, the presence of weak hhl reflections with odd h and l values indicates that refinements in the space group F23, which presume a checkerboard-like ordering of two types of subcells with slightly different atomic positions, are more appropriate. [ABSTRACT FROM AUTHOR]

The contamination by alumina crucible and the effect of Al impurity on the crystal growth of Bi2Sr2CaCu2O8+δ are always a thorny problem. In this paper, to gain non-aluminum Bi2Sr2CaCu2O8+δ single crystals, we present a modified self-flux method. From a cost point of view, the modified self-flux method is faster and more convenient than others. The growth time of Bi2Sr2CaCu2O8+δ single crystals has declined to 40 h. And, there are no any other unidentified peaks or intergrowth phase in X-ray diffraction pattern of Bi2Sr2CaCu2O8+δ single crystals. Resistivity and magnetism measurements indicate that Bi2Sr2CaCu2O8+δ is a monophasic superconductor, and the superconducting transition temperature is at 88 K. The four wings of magnetization hysteresis curves are exactly symmetrical to the origin and represent the lab samples contain a bulk pinning, not any magnetic impurity or hidden phase in Bi2Sr2CaCu2O8+δ single crystal. Significantly, the scanning electron spectrum shows that alumina crucibles do not generate Al impurity and any other impurity element in the melts and crystals. [ABSTRACT FROM AUTHOR]

In this study, structural and electrical transport properties of FeTe0.5Se0.5 system (FeTe0.5Se0.5+%1, FeTe0.5Se0.5+%3, FeTe0.5Se0.5+%5) fabricated in single crystal form by Self-flux method. Indium, which has a very low melting temperature within the FeTe0.5Se0.5 system, has been found to act as a flux in crystal formation and exhibits a homogeneous distribution in the structure. However, as the In addition rate increased, the superconducting properties of the FeTe0.5Se0.5 system changed negatively. According to the addition rates, the best value, Tconset and Tczero values were found as 16.07 K and 14.80 K for sample with 1% In addition. For higher In addition rates, it was found that both values tended to decrease. Upper critical field values were calculated from magnetoresistance curves by Werthamer-Halfand-Hohenberg (WHH) equation and it was found that the best value was for the addition of 1% In, and it was observed that the value decreased for high addition rates. The vortex formation and mobility activation energy determined by Arrhenius equation was found to be 1822, 515, 457 eV for samples with 1%, 3% and 5% In addition at zero Tesla. The obtained results showed that increasing rates of In addition to FeTe0.5Se0.5 system negatively affect the superconducting mechanism. [ABSTRACT FROM AUTHOR]

We investigate the single crystal growth of rutheno-cuprates, which are known to be magnetic superconductors. We attempted the single crystal growth of two systems, RuSr2GdCu2O8−δ (RuGd-1212) and RuSr2(Gd,Ce)2Cu2O10−δ (RuGd-1222), by the self-flux method with alumina boats. Fine cubic crystals of RuGd-1212 with a side length of approximately 5 μ m were obtained by slow cooling from 1350 to 940 ∘C. Plate-like RuGd-1222 crystals with a smooth plane were obtained at the surface of the precursor pellet. RuGd-1222 was more stable at high temperatures than RuGd-1212 and was also superconductive, but its superconductivity weakened as the cooling rate decreased. This weakening was induced by decomposition. Therefore, high-quality RuGd-1222 single crystals were difficult to obtain, and we failed to extract only the smooth planar crystal part. As a modified synthesis technique, we mixed a precursor containing Ru–Sr–Gd–Ce flux with RuGd-1222 powders and gradually cooled the mixture from 1350 to 1090 ∘C. A plate-like RuGd-1222 sample with a smooth surface and a size of 70 × 30μm2 was obtained from the side surface of the precursor pellet. By this technique, we could separate the planar crystal part. Semiquantitative composition analysis confirmed this planar crystal as a RuGd-1222 phase. The X-ray diffraction peak suggested the (0014) plane, implying that the plate-like precipitates are c-axis-oriented RuGd-1222 single crystals. [ABSTRACT FROM AUTHOR]

Abstract Using the flux method, we successfully synthesized Co-substituted Ca–La magnetoplumbite-type ferrite single crystals, Ca x La y Fe z Co w O 19 (Ca–La–Co system), a base material for high-performance hard ferrite magnets. Wavelength-dispersive X-ray analysis revealed that the chemical compositions of the obtained crystals depended on both the starting composition and reaction atmosphere. The fraction of Fe + Co to Ca + La deviates from the canonical value of 12, and the Co content, which is essential in magnetic anisotropy, improves with the synthesis under an oxygen gas stream. In addition, the magnetic anisotropy is enhanced by the Co substitution, as expected, but also depends on the Ca/La ratio, suggesting an appreciable effect of Fe 2 +. The magnetocrystalline anisotropy can be larger in the Ca–La–Co system than in the Sr–La–Co system. Graphical abstract Anisotropy field, H A , at 5 K for the Co-substituted Ca–La magnetoplumbite-type ferrite, Ca x La y Fe z Co w O 19 , plotted against Co content w. Literature data of the Sr–La–Co system are also plotted for comparison. fx1 Highlights • Successful synthesis of Co-substituted Ca-La magnetoplumbite-type ferrite single crystals. • Enhancement in the magnetic anisotropy by the Co substitution. • Magnetocrystalline anisotropy larger than the Sr-La-Co ferrites. [ABSTRACT FROM AUTHOR]

The cation compositions in the Ca–La magnetoplumbite-type (M-type) ferrite, Ca x La y Fe z O 19 , prepared from various initial fractions of reagents, were analyzed by wavelength-dispersive X-ray (WDX) spectroscopy. The reliability of the WDX composition analysis was confirmed by a crosscheck using inductively coupled plasma atomic emission spectrometry (ICP-AES). For particular polycrystalline samples furnace-cooled from 1250 ° C , the solubility ranges of Ca, La, and Fe were found to be 0.45 ≤ x ≤ 0.70 , 0.39 ≤ y ≤ 0.66 , and 11.82 ≤ z ≤ 11.92 , respectively, assuming x + y + z = 13 . Despite that the samples were synthesized from various starting compositions, the values of z / ( x + y ) of the matrix M phase are smaller than the M-type regular value, 12, for all the samples and comes in a very limited range at ∼ 11 , suggesting most probably Ca occupation at particular Fe sites or Fe deficiency due to insertion of stacking fault to Ca/La/O packing. Single crystals of Ca x La y Fe z O 19 with various x / y ratios were synthesized successfully by the self-flux method, followed by the characterization of their magnetic properties. The saturation magnetization and the Curie temperature were found to be almost independent of the cation composition. In contrast, the hard-axis magnetization process at low temperature depended significantly on the Ca/La ratio, and showed a sharp jump at ≲ 10 kOe, which can be attributed to a spin reorientation transition associated with the appearance of Fe 2 + . [ABSTRACT FROM AUTHOR]

In this study, we have systemically studied the physical, electrical and magnetic properties of Fe 0.99 Te 0.63 Se 0.37 single crystalline samples prepared by self-flux method. We found that the self-flux method is a suitable synthesis technique for this alloys if setting of experimental parameters made carefully. The M-H curve affirms that samples are typical type-II superconductor. Strong sign of bulk superconductivity, even after high field measurements, were seen. Calculated J c mag values, at zero field, were found to be 7.7 × 10 5 Acm −2 and 2.6 × 10 4 Acm −2 for 5 K and 10 K respectively. The upper critical field H c2 (0) has been determined with the magnetic field parallel to the sample surface and yielding a maximum value of 65 T. At the zero field coherence length, ξ , value was calculated to be 2.24 nm for 10% T c offset which is significantly larger (approximately 6 fold) than the unit cell, a , and indicating the absence of weak link behavior in the sample. Calculated μ 0 H c2 (0)/ k B T c rate indicated comparably higher value (3.66 T/K) than the Pauli limit (1.84 T/K) and obtained results were suggested unconventional nature of superconductivity in our samples. [ABSTRACT FROM AUTHOR]

We have reported the synthesis and characterization of FeTeSe prepared by self-flux technique with two different cooling rates, namely 0.8 and 4.5C/h. The effect of cooling rate on the samples has been characterized by using scanning electron microscopy (SEM) together with energy dispersive X-ray (EDX) spectrometer, X-ray diffraction (XRD), magnetization and magnetic hysteresis techniques. Four strong peaks were observed in the powder XRD patterns of both samples corresponding to the reflected intensities from the (001), (002), (003), and (004) planes of the tetragonal structure having space group P4/nmm. However, sample 2 has extra peaks corresponding to various non-superconducting binary phases of FeSe and FeTe. It can be concluded that the multiphase behavior of system increases with increasing cooling rate. The critical current value at 5 K, J (0), deduced from the M − H loops is approximately 5.6 × 10 A/cm for sample 1 and 7.5 × 10 A/cm for sample 2. Increasing in the critical current value can be attributed to non-superconducting binary phases acting as effective pinning centers in the system. [ABSTRACT FROM AUTHOR]

High-quality Bi2Sr2CaCu2O8+δ (Bi-2212) single crystals were grown by a self-flux method without mixing and grinding of the reagent of starting powders, to simplify the growth process of the crystals. During the crystal growth process, a pressure (<0.4 N/cm2) was applied using a brick placed on the cap on an alumina crucible. We obtained high-quality single crystals with zero-resistance transition temperature Tc,zero≈90 K in the best sample. The Bi-2212 intrinsic Josephson junctions (IJJs) were fabricated using standard photolithographic and Ar-ion milling techniques. Multi-branch structures were clearly observed in the I–V curves of the Bi-2212 IJJs. The critical current of the junction was sensitive to external magnetic-fields parallel to the a–b plane at temperature up to 89 K. [Copyright &y& Elsevier]