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Here, we report successful single crystal growth of new possible magnetic topological insulator (MTI) FeBi2Te4 by a self-flux method via a vacuum encapsulation process. The detailed Rietveld analysis of powder XRD data shows the as-grown MTI crystal to be mainly dominated by the FeBi2Te4 phase along with minority phases of Bi2Te3 and FeTe. Scanning electron microscope (SEM) image shows the morphology of as-grown MTI single crystal to be of layered type laminar structure. Raman spectroscopy of the crystal exhibited three distinct phonon modes at 65, 110, and 132 cm−1 along with two split secondary modes at 90, and 144 cm−1. The secondary split modes are the result of FeTe intercalation in the Bi2Te3 unit cell. Magnetoresistance (MR%) measurement has been performed at different temperatures, i.e., 200 K, 20 K, and 2 K in applied magnetic fields up to ± 12 Tesla, which showed very low MR in comparison with pure Bi2Te3 crystal. Temperature dependence of DC magnetization measurements shows the FeBi2Te4 crystal to be mainly of ferromagnetic (FM) or ferrimagnetic nature above 295 K, albeit a secondary weak magnetic transition is seen at 54–46 K as well. Detailed isothermal magnetization (MH) results showed that the FM saturation moment at 295 K is 0.00213 emu/g, which is nearly invariant until 400 K. In summary, we had grown an MTI FeBi2Te4 single crystal, which may be a possible entrant for the quantum anomalous Hall (QAH) effect at room temperature or above. [ABSTRACT FROM AUTHOR]

We report successful growth of magnetic topological insulator (MTI) MnBi2Te4. The heating schedule basically deals with growth of the crystal from melt at 9000C and very slow cooling (10C/hr) to around 6000C with 24 hours hold time, followed by cooling to room temperature. Our detailed, PXRD Reitveld analysis showed that the resultant crystal is dominated mainly by MnBi2Te4 and minor phases of Bi2Te3 and MnTe. The transport measurements showed a step like behavior at around 150 K followed by cusp like structure in resistivity at around 25 K (TP) due reported anti-ferromagnetic ordering of Mn. Both the resistivity transitions are seen clearly in dρ/dT measurements at 150 K and 20 K, respectively. The 25 K transition of the compound is also seen in magnetic susceptibility. Low temperature (5 K) magneto-resistance (MR) in applied field of up to 6 Tesla exhibited –ve MR below 3 Tesla and + ve for higher fields. Also, seen are steps in MR below 1 Tesla. The studied MnBi2Te4 MTI crystal could be a possible candidate for quantum anomalous Hall (QAH) effect. [ABSTRACT FROM AUTHOR]

In this letter, we present the superconducting property characterization of a phase pure, reasonably good quality YBaCuO sample. Studied compound is crystallized in orthorhombic Pmmm space group with lattice parameters a, b, and c being 3.829(2), 3.887(1) and 11.666(3) Å, respectively. Bulk superconductivity is observed below 90 K as evidenced by resistivity and dc/ ac magnetization measurements. The resistivity under magnetic field ( ρTH) measurements showed clearly both the intra-grain and inter-grain transitions, which are supplemented by detailed (of varying frequency and amplitude) ac susceptibility studies as well. The upper critical field at 0 K, i.e. H(0) being determined from ρTH measurements with 50 % criteria of resistivity drop, is ∼70 T. Studied polycrystalline YBaCuO is subjected to detailed heat capacity ( C) studies. C exhibited well-defined anomaly at below 90 K, which decreases with applied field. Although the C anomaly/peak at T reduces with applied field, the same is not completely suppressed in high applied fields of up to 12 T. The Sommerfeld constant ( γ) and Debye temperature ( Θ), as determined from low temperature fitting of C( T) data to Sommerfeld-Debye model, are 10.65 mJ/mole-K and 312.3 K, respectively. The results are compared with existing literature on bulk polycrystalline superconducting YBaCuO sample. [ABSTRACT FROM AUTHOR]

We report the effect of silver addition on superconducting performance of bulk YBCO (YBaCuO) superconductor. All the studied samples are prepared by conventional solid-state reaction method. Rietveld fitted X-ray diffraction data confirmed the single phase formation for all the studied samples. Detailed AC susceptibility measurements as a function of driven AC amplitude (1 Oe-17 Oe) of these samples revealed the enhancement of grains coupling with increasing Ag content in YBCO + Ag composite system. 10 wt% Ag added YBCO superconductors exhibited the optimal intergranular coupling. The Scanning Electron Microscopy (SEM) observations indicate an increase in the grains connectivity in terms of narrow grain boundaries for doped samples. The average grain size is found to increase with Ag doping. It is concluded that limited addition of Ag in bulk YBCO superconductor significantly improves the grains coupling and, as a result, the optimal superconducting performance. YBCO + Ag composites could prove to be potential candidates for bulk superconducting applications of the studied high- T system. [ABSTRACT FROM AUTHOR]

We study the structural and bulk superconducting properties of self-flux grown PdBi2Te3 single crystal. Phase purity of as grown crystal is confirmed by Rietveld refinement of gently crushed powder XRD of the same. PdBi2Te3 crystallizes in rhombohedral structure with R-3 m space group along with small impurity of Bi. Scanning electron microscopy (SEM) images showed layered structure and the elemental analysis by energy dispersive X-ray analysis (EDAX) done on same confirmed the stoichiometry to be near to PdBi2Te3. Characteristic vibrational modes, viz., A11g, Eg2, and A21g, are clearly observed in Raman spectrum and are slightly shifted from that as in case of Bi2Te3. Bulk superconductivity is confirmed by FC and ZFC magnetization measurements (M-T) exhibiting diamagnetic transition with Tconset at around 6 K. M-H plots at different temperatures of 2 K, 2.5 K, 3 K, 3.5 K, 4 K, 4.5 K, 5 K, and 6 K showed clear opening of the loop right up to 6 K. Both M-T and M-H clearly establish the appearance of bulk type II superconductivity below 6 K in studied PdBi2Te3. The lower critical field Hc1 and upper critical field Hc2 are at 180 Oe at 4800 Oe, respectively, at 2 K for as grown PdBi2Te3 crystal. Other critical parameters of superconductivity such as coherence length, penetration depth and kappa parameter are also calculated. [ABSTRACT FROM AUTHOR]

We report an easy and versatile route for the synthesis of the parent phase of the newest superconducting wonder material, i.e., p-terphenyl. Doped p-terphenyl has recently shown superconductivity with transition temperature as high as 120 K. For crystal growth, the commercially available p-terphenyl powder is pelletized, encapsulated in an evacuated (10 Torr) quartz tube and subjected to high-temperature (260 C) melt followed by slow cooling at 5 C/h. A simple temperature-controlled heating furnace is used during the process. The obtained crystal is one piece, shiny, and plate like. Single crystal surface XRD (X-ray diffraction) showed unidirectional (00 l) lines, indicating that the crystal is grown along the c-direction. Powder XRD of the specimen showed that as grown p-terphenyl is crystallized in monoclinic structure with space group P2 /a space group, having lattice parameters a = 7.672 (2) Å, b = 5.772 (5) Å, and c = 13.526(3) Å and β = 91.484 (3). Scanning electron microscopy (SEM) pictures of the crystal showed clear layered slab-like growth without any visible contamination from oxygen. Characteristic reported Raman active modes related to C-C-C bending, C-H bending, C-C stretching, and C-H stretching vibrations are seen clearly for the studied p-terphenyl crystal. The physical properties of the crystal are yet underway. The short letter reports an easy and versatile crystal growth method for obtaining quality p-terphenyl. The same growth method may probably be applied to doped p-terphenyl and to subsequently achieve superconductivity to the tune of as high 120 K for the newest superconductivity wonder, i.e., high- T organic superconductor (HTOS). [ABSTRACT FROM AUTHOR]