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Abstract: We present detailed magnetization and magneto-transport studies on the title compound SmCoAsO. In a recent paper we reported (Awana et al., 2010 ) the complex magnetism of this compound. SmCoAsO undergoes successive paramagnetic (PM)–ferro-magnetic (FM)–anti-ferro-magnetic (AFM) transitions with decrease in temperature. This is mainly driven via the c-direction interaction of Sm4f (SmO layer) spins with adjacent (CoAs layer) ordered Co3d spins. In this article we present an evidence of kinetic arrest for FM–AFM transition. The isothermal magnetization (MH) loops for SmCoAsO exhibited the meta-magnetic transitions at 6, 8 and 10K at around 80, 60 and 50kOe fields, respectively, with characteristic hysteresis shoulders along with the non-zero moment at the origin, thus suggesting the possibility of kinetic arrest. Suggested kinetic arrest is further evident in zero field-cooled (ZFC) and field-cooled (FC) hysteresis under high fields of up to 140kOe magnetization (MT) and the magneto-transport measurements R(T)H during FM–AFM transition. The time dependent moment experiments exhibited very small (∼2–3%) increase of the same below 20kOe and decrease for 30kOe at 15K. [Copyright &y& Elsevier]

Abstract: Here, we report the synthesis and characterization of sulphur-substituted iron telluride i.e. FeTe1− x S x ; (x =0–30 %) system and study the impact of low temperature oxygen (O2) annealing as well. Rietveld analysis of room temperature X-ray diffraction (XRD) patterns shows that all the compounds are crystallized in a tetragonal structure (space group P4/nmm) and no secondary phases are observed. Lattice constants are decreased with increasing S concentration. The parent compound of the system i.e. FeTe does not exhibit superconductivity but shows an anomaly in the resistivity measurement at around 78K, which corresponds to a structural phase transition. Heat capacity C p(T) measurement also confirms the structural phase transition of FeTe compound. Superconductivity appears by S substitution; the onset of superconducting transition temperature is about 8K for FeTe0.75S0.25 sample. Thermoelectric power measurements S(T) also shows the superconducting transition at around 7K for FeTe0.75S0.25 sample. The upper critical fields Hc 2(10%), Hc 2(50%) and Hc 2(90%) are estimated to be 400, 650 and 900 kOe respectively at 0K by applying Ginzburg Landau (GL) equation. Interestingly, superconducting volume fraction is increased with low temperature (200°C) O2 annealing at normal pressure. Detailed investigations related to structural (XRD), transport [S(T), R(T)H], magnetization (AC and DC susceptibility) and thermal [C p(T)] measurements for FeTe1− x S:O2 system are presented and discussed. [Copyright &y& Elsevier]

Abstract: We report the synthesis, magnetic susceptibility and crystal structure analysis for samples. The study helps find a correlation among the lattice parameters, chemical composition and the superconducting transition temperature . Rietveld analysis is done on the -ray diffraction patterns of all synthesized samples to determine the lattice parameters. The parameter decreases slightly and has a random variation with increasing , while parameter increases from 3.26 for pure NbB2 to 3.32 for i.e. NbB2.4. With higher Boron content the parameter decreases slightly. The stretching of lattice in direction induces superconductivity in the non-stoichiometric niobium boride. Pure NbB2 is non-superconductor while the other samples show diamagnetic signal in the temperature range 8.9–11 K. Magnetization measurements () at a fixed temperature of 5 K are also carried out in both increasing and decreasing directions of field. The estimated lower and upper critical fields ( & ) as viewed from plots are around 590 and 2000 Oe, respectively, for NbB2.6 samples. In our case, superconductivity is achieved in NbB2 by varying the Nb/B ratios, rather than changing the processing conditions as reported by others. [Copyright &y& Elsevier]

Abstract: The physical property characterization of Al doped Mg1− x Al x B2 system with x =0.0 to 0.50 is reported. The results related to phase formation, structural transition, resistivity ρ(T) and magnetization M(T) measurements are discussed in detail. It is shown that the addition of electrons to MgB2 through Al results in loss of superconductivity. Also seen is a structural transition associated with the collapse of boron layers reflected by the continuous decrease in the c parameter. The main emphasis in this paper is on slow scan X-ray diffraction (XRD) results, which confirm the existence of a superstructure along the c-direction for the x =0.50 sample. The appearance of some additional peaks, viz. [103], [004], [104] and [112], results in doubling of the lattice parameter along the c-axis. This possibly indicates the alternative ordering of Al and Mg in MgAlB4 separated by hexagonal boron layers but still maintaining the same hexagonal AlB2 type structure. [Copyright &y& Elsevier]

Abstract: We report on the synthesis, phase formation, microstructure, and magnetization, of nano(n)-TiO2-added MgB2 polycrystalline compounds. The added n-TiO2 amounts are varied from 1% to 15% in weight (wt). All the studied samples are near single phase with small amounts of un-reacted Mg/MgO up to 10wt%. The 15wt% n-TiO2 added sample seems to be a multi-phase compound with unusual broadening of the main MgB2 reflection and additional unidentified lines in its X-ray diffraction (XRD) pattern. The superconducting transition temperature (T c), as measured by magnetization experiments, decreases marginally with n-TiO2 addition, for example the T cs are at 37.5K and 35.5K, respectively, for pristine and 10wt% n-TiO2-added samples. This indicates that Ti has not significantly substituted into the host MgB2 lattice. The grain morphology of these compounds reveals porous regions and does not change much with TiO2 addition. High resolution transmission electron microscopy (HRTEM) studies revealed the presence of n-TiO2 in these samples. The critical current density (J c) of the MgB2–n-TiO2 samples, as estimated using the Bean model, shows better performance under magnetic fields above 3T than pristine MgB2 for up to 4wt% of addition, and decreases rapidly for additions above 6wt%. We conclude that n-TiO2 helps in enhancing the flux pinning centers in MgB2 superconductor and hence improves the J c(H) performance for additions up to 4wt% in fields above 3T. [Copyright &y& Elsevier]

Abstract: We report the synthesis and magnetization of Sr2RuREO6 (RE/Ru-211O6) with RE=Gd and Eu. Both Gd and Eu/Ru-211O6 are formed in distorted perovskite-type single phase with monoclinic P21/n space group. Magnetization (M/T) measurements exhibited antiferromagnetic ordering of Ru moments for both Gd and Eu compounds at a T N of around 30K due to super-exchange Ru–O–O–Ru interaction. Interestingly enough, detailed M/H plots of Gd/Ru-211O6 exhibited the development of a ferromagnetic (FM) component at 20K. Furthermore, below 10K, the FM component disappears, and rather spin freezing field (H SF) of around 1000Oe is seen at 5K. In case of Eu/Ru-211O6, the basic antiferromagnetic ordering of Ru moments remains invariantly down to 5K, and the appearance of the FM component is not seen. It seems that the high magnetic moment of 8μ B for Gd3+ influences the anti ferromagnetic (AFM) ordering of Ru in case of Gd/Ru-211O6. [Copyright &y& Elsevier]

Abstract: Detailed X-ray diffraction studies on RuSr2Eu1.5Ce0.5Cu2O10−δ (Eu–Ru-1222) magneto superconductor down to 13K at close temperature intervals revealed that with decreasing temperature, the c-parameter decreases linearly down to 100K, following the relation c =28.412(1)+2.5(1)×10−4 T and then becomes almost temperature independent on further lowering of temperature. Interestingly, the linear decrease in the a-parameter is seen only up to 180K. Below 180K, the observed values of the a-parameters are more than the value expected from the linear variation. This departure can be considered as development of strain in the system. Interestingly enough, these temperatures coincide with the complex magnetic ordering (T mag) of Ru in Ru-1222 system. This is the first report of the observation of the onset of excess volume and also of the strain along the a-axis near the magnetic ordering temperature in Ru-1222 superconductor, and indicates a coupling between the lattice and the magnetism in this system. Magnetization, magneto transport and thermoelectric power measurements being carried out on the same sample are also reported. The results of low temperature excess volume and the strain along a-axis of Ru-1222 compound are reportedly not seen in Ru-1212 (RuSr2GdCu2O8). [Copyright &y& Elsevier]

Abstract: We report the phase formation, and present a detailed study of magnetization and resistivity under magnetic field of MgB2 polycrystalline bulk samples prepared by the Fe-tube encapsulated and vacuum (10−5 Torr) annealed (750 ∘C) route. Zero-field-cooled magnetic susceptibility measurements exhibited a sharp transition to the superconducting state with a sizeable diamagnetic signal at 39 K . The measured magnetization loops of the samples, despite the presence of flux jumps, exhibited a stable current density of around 2.4×105 A/cm2 in up to 2 T (Tesla) field and at temperatures up to 10 K. The upper critical field is estimated from resistivity measurements in various fields and shows a typical value of 8 T at 21 K. Further, measurements at an applied field of 0.1 T reveal a paramagnetic Meissner effect (PME) that is briefly discussed. [Copyright &y& Elsevier]

The results of micro-structural and detailed magnetization studies are reported here for our recently published TbSr2Cu2.7Mo0.3O7+δ superconductor with a transition temperature (Tc) at as high as 80K [V.P.S. Awana, A. Gupta, H. Kishan, E. Takayama-Muromachi, T. Watanabe, M. Karppinen, H. Yamauchi, S.K. Malik, W.B. Yelon, V. Ganesan, A.V. Narlikar, Solid State Commun. 129 (2003) 117]. From XRD and EDX the sample was confirmed to be of single-phase and possess the nominal cation stoichiometry. The SEM images showed well-developed grains for this ceramic high-Tc superconductor. Magnetization measurements at various temperatures and fields revealed bulk superconductivity below 80K. Magnetization versus applied field (M vs H) loops at various temperatures below the Tc exhibited clear full penetration field HP. In normal state (>100K) the susceptibility follows the Curie–Weiss behavior with an effective paramagnetic moment of 9.83μB. [Copyright &y& Elsevier]

The samples of composition RuSr2(Ln3/4Ce1/4)2Cu2O10 with Ln=Ho, Y and Dy, being synthesized by high-pressure high-temperature (6 GPa, 1200 °C) solid-state synthesis route do crystallize in space group I4/mmm. These samples exhibit magnetic transitions at ∼150 K with significant branching of zero-field-cooled (zfc) and field-cooled (fc) magnetization and a sharp cusp in zfc at ∼100 K, followed by a possible superconducting transition at lower temperatures. All the compounds show typical ferromagnetic hysteresis loops in magnetic moment (M) vs. field (H) magnetization at 5 K. Near saturation of the moments at 5 K is achieved in above 5 T (Tesla) applied fields with a value of ∼0.80μB. At low temperatures (5 K) these compounds exhibit both superconductivity and ferromagnetism. To our knowledge these are first successfully synthesized Ru-1222 compounds with various lanthanides including Y, Dy, and Ho. The results are compared with widely reported Gd/Ru-1222 compound. [Copyright &y& Elsevier]

Samples of the composition CoSr2YCu2O7−δ (Co-1212) were synthesized in a single-phase form and studied using neutron diffraction (ND), chemical analyses and magnetization measurements. The structure of Co-1212 is best described in the space group Ima2 that yields good fit to the observed ND data. No cross-migration between Cu and Co is seen for Co-1212. The overall oxygen content, as determined from the refined oxygen occupancies, comes out to be around 7.0. This is close to the values determined from wet-chemical and thermogravimetric analyses. Unlike in Cu-1212, the complete reduction of Co-1212 in 5% H2/95% Ar atmosphere occurs in a single step, revealing that the amount of reversibly removable oxygen is considerably less than that in Cu-1212. Zero-field-cooled and field-cooled magnetizations, measured in an applied field of 100 Oe, show branching at around 30 K, presumably due to the magnetic ordering of Co moments. The present Co-1212 sample is found not to be superconducting down to 5 K. [Copyright &y& Elsevier]

Samples of the composition CoSr2YCu2O7−δ (Co-1212) were synthesized in a single-phase form and studied using neutron diffraction (ND), chemical analyses and magnetization measurements. The structure of Co-1212 is best described in the space group Ima2 that yields good fit to the observed ND data. No cross-migration between Cu and Co is seen for Co-1212. The overall oxygen content, as determined from the refined oxygen occupancies, comes out to be around 7.0. This is close to the values determined from wet-chemical and thermogravimetric analyses. Unlike in Cu-1212, the complete reduction of Co-1212 in 5% H2/95% Ar atmosphere occurs in a single step, revealing that the amount of reversibly removable oxygen is considerably less than that in Cu-1212. Zero-field-cooled and field-cooled magnetizations, measured in an applied field of 100 Oe, show branching at around 30 K, presumably due to the magnetic ordering of Co moments. The present Co-1212 sample is found not to be superconducting down to 5 K. [ABSTRACT FROM AUTHOR]

Abstract: Temperature dependence of magnetic susceptibility χ(T) of a pure polycrystalline RuSr2(Eu1.5Ce0.5)Cu2O10 compound in the zero-field-cooled (ZFC) and the field-cooled branches deviate below 150K with a sharp upward turn around 100K. At lower temperatures the ZFC branch shows a cusp at T cusp =75K, a superconducting transition temperature at T c =25K. χ(T) becomes negative around 20K. Isothermal ferromagnetic M(H) loops are observed up to 80K. At 5K, the remanent magnetization and the coercive fields (H c) are 0.6Bohr magnetons and 300Oe, respectively. With increasing T, the H c does not decrease monotonically as expected for normal FM domains, but in an anomalous way with a peak around 80K before collapsing above 150K. Electron spin resonance (ESR) measurements show clear ferromagnetic resonances (FMR) at applied fields of 5mT. Interestingly enough the change in FMR intensity also exhibits a peak around 80K, the same as for H c. [Copyright &y& Elsevier]

Provides information on a study that investigated the magnetization and heat capacity of the perovskite compound, R...Sr...FeO... with R = La and Pr. Experimental details; Results and discussion on the study; Conclusion.

Highlights: [•] With increase in Bi-doping, TMI of Pr0.6-xBi x Sr0.4MnO3 manganites decreases. [•] It is observed that these compounds have low thermal conductivity. [•] All compounds show peaks in specific heat at their transitions. [•] Small polaron hopping model is operative in the high temperature insulating region. [ABSTRACT FROM AUTHOR]

Abstract: We report structural, DC magnetization, linear and non-linear AC susceptibility for phase pure RuSr2Y1.5Ce0.5Cu2O10 (YRu-1222) magneto-superconductor. The studied compound is synthesized through HPHT (high pressure high temperature: 6GPa, 1400°C) technique at NIMS-Japan. As synthesized YRu-1222, is crystallized in single phase tetragonal structure with space group I4/mmm. DC magnetic susceptibility showed that studied YRu-1222 is a magneto-superconductor with Ru spins magnetic ordering at around 120K and superconductivity in the Cu-O2 planes below ∼40K. The frequency and field dependent AC susceptibility measurements confirmed the spin-glass (SG) behavior with homogenous/non-homogenous ferromagnetic clusters for the studied system. The frequency variation followed the Vogel–Fulcher law with homogeneous/non-homogenous magnetically interacting ferromagnetic clusters embedded in spin-glass (SG) matrix. Detailed linear and non-linear AC susceptibility measurements are carried out to probe the exact magnetic nature of the studied magneto-superconductor YRu-1222. [Copyright &y& Elsevier]

We address the effect of MgO impurity on the superconducting properties of MgB 2 . The synthesis of MgB 2 is very crucial because of sensitivity of Mg to oxidation which may lead to MgO as a secondary phase. Rietveld refinement was performed to determine the quantitative volume fraction of MgO in the samples synthesized by two different techniques. Both the samples were subjected to magnetization measurements under dc and a.c. applied magnetic fields and the observed results were compared as a function of temperature. Paramagnetic Meissner effect has been observed in a sample of MgB 2 having more amount of MgO (with T c = 37.1 K) whereas the pure sample MgB 2 having minor quantity of MgO shows diamagnetic Meissner effect with T c = 38.8 K. M – H measurements at 10 K reveal a slight difference in irreversibility field which is due to MgO impurity along with wide transition observed from ac magnetic susceptibility measurements. The magnetotransport measurements ρ ( T ) using ρ N = 90%, 50% and 10% criterion on pure sample of MgB 2 has been used to determine the upper critical field whereas the sample having large quantity of MgO does not allow these measurements due to its high resistance. [ABSTRACT FROM AUTHOR]

Abstract: Doping effect of ZnO-nanoparticles on the superconducting properties of MgB2 has been studied. The 2% nano-ZnO doped MgB2 shows the excellent J c and H irr at all temperatures and magnetic fields amongst the doped and undoped sample. The lattice parameter-c shows the higher value for 2% ZnO doped MgB2 sample, which clearly demonstrates the presence of the lattice strain in doped samples. The residual resistivity ratio was increased as the nano-ZnO doping level increased. Very slight variation in T c is observed from the temperature dependence of resistivity plot of nano-ZnO doped MgB2. In M (H) plot at low applied fields, we have observed large vortex instabilities (vortex-avalanches) associated with 2% and 4% doped samples. Vortex avalanche effect is diminishes with increasing temperature and disappears near 15K. The results are discussed in terms of local-vortex instabilities caused by doping of ZnO nanoparticles. Scanning electron microscopy studies show that the synthesized samples are well adherent and grains are uniformly distributed with an average particle size of ∼5–10μm. [Copyright &y& Elsevier]

Abstract: Bulk polycrystalline Ni-substituted SmFe1−x Ni x AsO (x = 0.0–1.0) samples are synthesized by solid state reaction route in an evacuated sealed quartz tube. The cell volume decreases with increase of Ni content in SmFe1−x Ni x AsO, thus indicating successful substitution of smaller ion Ni at Fe site. The resistivity measurements showed that the spin density wave (SDW) transition is suppressed drastically with Ni doping and subsequently superconductivity is achieved in a narrow range of x from 0.04 to 0.10 with maximum Tc of 9K at x = 0.06. For higher content of Ni (x ≥ 0.10), the system becomes metallic and superconductivity is not observed down to 2K. The magneto-transport [R(T)H] measurements exhibited the upper critical field [Hc2(0)] of up to 300 kOe. The flux flow activation energy (U/kB) is estimated ∼98.37K for 0.1T field. Magnetic susceptibility measurements also confirm bulk superconductivity for x = 0.04, 0.06 and 0.08 samples. The lower critical field (Hc1) is around 100 Oe at 2K for x = 0.06 sample. Heat capacity CP(T) measurements exhibited a hump like transition pertaining to SDW in Fe planes at around 150K and an AFM ordering of Sm spins below temperature of 5.4K for ordered Sm spins [TN(Sm)]. Though, the SDW hump for Fe spins disappears for Ni doped samples, the TN (Sm) remains unaltered but with a reduced transition height, i.e., decreased entropy. In conclusion, complete phase diagram of SmFe1−x Ni x AsO (x = 0.0–1.0) is studied in terms of its structural, electrical, magnetic and thermal properties. [Copyright &y& Elsevier]

Abstract: We report DC isothermal magnetization, global critical current density (JC ), Intra-grain critical current density () and resistive upper critical field (Bc2 ) of polycrystalline Y1− x Ca x Ba2Cu3O7−δ (YBCO); x =0.00, 0.05, 0.10, 0.15, 0.20 and 0.25. Ca doping at Y sites in YBCO superconductor results in flux pinning property, which can enhance the critical current densities and upper critical fields. JC and are experimentally calculated through DC isothermal magnetization measurement (M–H), employing the well known Bean’s critical model. It is observed that both type of current densities (global and intra) enhance in lower doped (5%) samples and can be accounted in terms of reaching maximum of pinning centers and improved grain couplings nature. The upper critical field (Bc2 ) increases with Ca content being consistent with enhanced grain coupling nature of doped samples. [Copyright &y& Elsevier]

Abstract: The magnetic and magnetocaloric properties of polycrystalline La0.70(Ca0.30−x Sr x )MnO3:Ag 10% manganite have been investigated. All compositions are crystallized in single phase orthorhombic Pbnm space group. Both, the insulator–metal transition temperature (T IM ) and Curie temperature (T c ) are observed at 298K for x=0.10 composition. Though both T IM and T c are nearly unchanged with Ag addition, the MR is increased. The MR at 300K is found to be as large as 31% with magnetic field change of 1T, whereas it reaches up to 49% at magnetic field of 3T for the La0.70Ca0.20Sr0.10MnO3:Ag0.10 sample. The maximum entropy change (ΔS Mmax ) at near its T c (300.5K) is 7.6Jkg−1 K−1 upon the magnetic field change of 5T. The La0.70Ca0.20Sr0.10MnO3:Ag0.10 sample having good MR (31%1T, 49%3T) and reasonable change in magnetic entropy (7.6Jkg−1.K−1, 5T) at 300K can be a potential magnetic refrigerant material at ambient temperatures. [Copyright &y& Elsevier]

Abstract: We report synthesis, structural and magnetic (DC and AC) properties of Boron substituted MgCNi3 superconductor. A series of polycrystalline bulk samples Mg1.2C1.6−x B x Ni3 (x=0.0, 0.08 and 0.16) is synthesized through standard solid-state reaction route, which are found to crystallize in cubic perovskite structure with space group Pm3m. Rietveld analysis of observed XRD data show that lattice parameters expand from a=3.8106 (4)Å for pure, to 3.8164 (2)Å and 3.8173 (5)Å for 5% and 10% Boron substituted samples respectively. DC magnetization exhibited superconducting transition (T c ) at around 7.3K for pure sample, and the same decreases slightly with Boron substitution. The lower critical field (H c1) at 2K is around 150Oe for pure sample, which increases slightly with Boron substitution. For pure sample the upper critical field (H c2) being determined from AC susceptibility measurements is 11.6kOe and 91.70kOe with 50% and 90% diamagnetism criteria respectively, which decreases to 5.57kOe and 42.5kOe respectively for 10% Boron substituted sample. 10% Boron substitution at Carbon site has decreased both the H c2 and T c . On the other hand lower critical field (H c1) at 2K is slightly increased from around 150Oe for pure sample, to 200Oe for 10% Boron substituted sample. Seemingly, the Carbon site Boron substitution induced disorder though has increased slightly the H c1 but with simultaneous decrease in superconducting transition temperature (T c ) and upper critical field (H c2). The high relative proportion of Ni in studied MgCNi3 suggests that magnetic interactions are important and non-oxide perovskite structure make it interesting. [Copyright &y& Elsevier]

Abstract: In this paper we investigate the properties of polycrystalline series of Ru1− x Cr x Sr2Eu1.5Ce0.5Cu2O10− δ (0.0⩽ x ⩽0.40) by resistivity, XRD and dc magnetization measurements. EuRu-1222 is a reported magneto superconductor with Ru spins magnetic ordering at temperatures near 100K and superconductivity occurs in Cu–O2 planes below T c ≅40K. The exact nature of Ru spins magnetic ordering is still being debated and no conclusion has been reached yet. In this work, we found the superconducting transition temperature T c =20K from resistivity and dc magnetization measurements for pristine sample. DC magnetization measurements exhibited ferromagnetic like transition for all samples. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we report the change in electronic structure of Cu0.3Co0.7Ba2−x Sr x YCu2O7+δ with change in structural pressure. Rietveld refined X-ray diffraction (XRD) pattern shows that the samples are phase pure. Decrease in lattice parameters with increasing x, confirms replacement by Sr ion at Ba ion site. The calculated tolerance factor of the systems is in accord with lattice parameter changes. The X-ray photoelectron spectroscopy (XPS) is made to find out the variation in ionic state of Co and Cu with ionic size variation in BaO/SrO layers. Effect of the same on the electronic structure and transport properties is explored. The XPS measurement reveals that Cu is in mixed 1+/2+ state and variation in valence state is non-monotonous with increasing x. Whereas Co is in mixed 3+/4+ state and with increasing x its valence state is increasing. The observed changes in electronic structure are subject of structural changes. The resistivity measurement shows that normal state conductivity decreases with increasing x. Resistivity behaviour indicates about holes in Cu/CoO x planes taking part in charge transport. The magnetic measurement (M–T and M–H) shows that paramagnetic nature for all the compositions. The presence of Cu ions in Cu/CoO x chains/planes results in paramagnetic behaviour. [Copyright &y& Elsevier]

Abstract: Comparative study on various systems originated from MSr2RECu2O z (M-1212; 0≤ δ <1) compounds (M=Al, Nb, Fe, Ru, Ga and Co and RE=Eu, Y) has been made. The Rietveld refinement is done for all samples on their respective X-ray diffraction (XRD) patterns, which showed that all compounds are crystallized in single phase. While, Nb-, Fe-, Ru- and Al-1212 possess tetragonal P4/mmm space group structure, the Ga-1212 and Co-1212 are crystallized in orthorhombic Ima2 space group. The change of space group from P4/mmm to Ima2 resulted in doubling of unit cell. The buckling angle [Cu2–O2–Cu2 angle] determined, showed that most of the studied samples are under doped and hence they lack superconductivity. Thermogravimetric analysis (TGA) showed the M-1212 compounds to be more stable than widely studied 90K superconductor Cu-1212 (RE-123). The magnetization behavior of Ga-, Nb- and Al-1212 follows a Curie–Weiss like behavior due to paramagnetic contribution of Cu. In case of Co-, Fe-1212 short magnetic correlations/spin-glass like features is seen below 100K. Different surface morphologies have been observed from the scanning electron microscopy (SEM) study of all the samples. Efforts are underway to dope mobile carriers in studied single phase under doped M-1212 (M=Ga, Nb, Fe, Al and Co) compounds and to introduce superconductivity in them. [Copyright &y& Elsevier]

Abstract: The structural magnetic and magneto-transport properties of double perovskite system Ba2− x Sr x FeMoO6 (0⩽x⩽1.0) prepared in bulk polycrystalline form are reported in this paper. X-ray diffraction analysis showed that samples are single phase and the lattice constants decreases with increase in the Sr content. The degree of Fe–Mo ordering has been found decreasing in the series with an increase in the Sr content. Parent compound Ba2FeMoO6 exhibits saturation magnetic moment value of 3.54μB/f.u. at 85K in a magnetic field of 6000Oe. Temperature dependence of resistivity shows metallic behavior for all the samples. The magneto-resistance (MR) of the compound with x=0.4 is higher than that of the other samples. At room temperature this system shows a saturation magnetization value of 1.73μB/f.u. and MR value of 7.08% (1T). The observed variations in the structural and magnetic properties are attributed to the change of chemical pressure due to the substitution of Sr in place of Ba. The effect of antisite disorder (ASD) defects on magneto-transport properties is studied in more detail. [Copyright &y& Elsevier]

Abstract: We report synthesis and superconductivity of Pb-1212–Cu1− x Pb x Sr2Y0.6Ca0.4Cu2O7 (x =0.5–0.9) compounds. These compounds were synthesized through solid-state reaction route with optimized sintering temperatures and conditions. In particular, one needs to employ reducing atmosphere conditions to achieve superconductivity in higher Pb content samples. The X-ray diffraction (XRD) patterns reveals that all the compounds are crystallized in space group P4/mmm RE-123 structure. Superconductivity at 56K (onset) is achieved for Pb content as high as 90%. Our study reveals that superconductivity and structure stabilization in Pb-based are more critical to synthesizing conditions than other cuprates. It is concluded that superconductivity can be introduced in Pb-1212 compounds by synthesizing the same in reducing atmosphere and thus the Pb in lower (<+4) valence state. This ensures the replacement of Cu–O x chains of RE-123 by Pb–O x sheets acting as charge reservoir carrier donating blocks. [ABSTRACT FROM AUTHOR]