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We investigate the magnetotransport properties of La0.7Ca0.3-xAgxMnO3 (0<=x<=0.3) polycrystalline films prepared by spray pyrolysis. The virgin La0.7Ca0.3MnO3 (LCMO) (x=0.0) film shows paramagnetic-ferromagnetic [insulator-metal (IM)] transition at TC∼260 K (TIM∼245 K). Ag doping induces appreciable enhancement in TC/TIM and interestingly TIM of Ag doped films is higher than the corresponding TC value. In the 30% Ag doped film IM transition occurs at ∼325 K which is ∼10 K higher than its TC∼315 K. Strong irreversibility is observed in zero field cooled–field cooled magnetization of all the films and the irreversibility temperature Tirr>TC increases with Ag doping. This suggests the formation of magnetic clusters above TC. The pure LCMO film exhibits small magnetoresistance (MR) ∼20% and rather poor temperature coefficient of resistance (TCR) in the vicinity of the room temperature. In contrast, around room temperature the Ag doped films show large MR which is ∼60% for x=0.15 and decreases to ∼30% for the pure Ag doped film. Ag doped films also have good TCR ∼4%/K in the vicinity of room temperature. [ABSTRACT FROM AUTHOR]

Various MSr[SUB2]Ycu[SUB2]O[SUBz] (M-1212 with M = Fe, Co, Al, and Ga) compounds have been synthesized through a solid-state reaction route. All these compounds are derived from the basic CuBa[SUB2]Ycu[SUB2]O[SUB7-δ] structure. Rietveld structural refinement of the room-temperature neutron diffraction data for Fe-1212 reveals that nearly half of Fe remains at the M site, while the other half goes to the Cu site in the CuO[SUB2] plane. For the M = Co, Al, and Ga compounds, the basic unit cell gets doubled due to two distinct M sites in the M-O layer and the space group Ima2, without any cation intermixing is found to be more appropriate. For the M = Fe sample, magnetic ordering of Fe spins is seen from magnetization data below 70 K. In the case of the M = Co compound, a shallow down-turn in magnetic susceptibility is seen below 150 K, indicating low-dimensional magnetic characteristics of the Co-O layer. The compounds with M = Al and Ga show paramagnetic behavior in their magnetization data down to 5 K. The oxygen content, established for each compound based on oxygen occupancies, refined from the neutron diffraction data comes close to 7.0 for each. [ABSTRACT FROM AUTHOR]

57Fe (1%) doped SrCoO3 obtained by high-pressure method, has been investigated by magnetization and Mössbauer spectroscopy studies (MS) in the temperature range 4.2 K to 300 K. The ferromagnetic ordering temperature T C obtained is 272(2) K. Isothermal magnetization curves have been measured at various temperatures, from which the saturation moments ( M sat) have been deduced. The 57Fe MS spectra display standard six-line patterns with an isomer shift typical of Fe3 + and a very small quadrupole splitting (QS = 0.14(1) mm/s above T C). The magnetic hyperfine field at 4.2 K is 276(1) kOe. The temperature dependencies of the iron hyperfine field and M sat (1.83 µ B at 5 K) are almost identical. This shows that the Fe3 + is replacing Co4 + , both of the same electronic configuration. They also interact similarly, namely the Fe–Co exchange is almost identical to the Co–Co exchange. [ABSTRACT FROM AUTHOR]

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]

In this paper, we report the synthesis, magnetotransport features, and magnetization of polycrystalline La2/3Ca1/3MnO3:Agx/Inx composites with x = 0, 0.1, 0.2, 0.3 and 0.4. In the case of La2/3Ca1/3MnO3:Agx, the temperature coefficient of resistance (TCR) near ferromagnetic (FM) transition enhances significantly with the addition of Ag. The FM transition temperature (TFM) is also increased slightly with Ag doping. Magnetotransport measurements revealed that magnetoresistance (MR) is found to be maximum near TFM. Very sharp TCR is seen near TFM with the highest value of up to 15 % for an Ag (0.4) sample, which is an order of magnitude higher than for pristine sample and is the best value yet reported for any polycrystalline LCMO compound. Increased TCR, TFM, and significant above room temperature MR of La2/3Ca1/3MnO3:Agx composites is explained on the basis of improved grains size. Interestingly the La2/3Ca1/3MnO3:Inx composites behaved exactly in the opposite way, resulting in decreased TFM, and TCR compared to the pristine LCMO compound. In fact, the grains morphology of LCMO:Inx composites is seen to be inferior to pristine LCMO which is opposite of the LCMO:Agx case. [ABSTRACT FROM AUTHOR]

NMR measurements have been performed on the ordered perovskite Sr2Cu(Re0.69Ca0.31)O6 which shows ferromagnetic (ferrimagnetic) properties below Tc∼440 K with spontaneous magnetization of about 0.25 μB per formula unit at 5 K. Two kinds of NMR lines showing large enhancement of NMR signals were observed at 5 K with H=0.5 T at the frequency range from 58 to 180 MHz, and each line was attributed to the Cu1 and Cu2 site. [Copyright &y& Elsevier]

57Fe (1%) doped SrCoO3 obtained by high-pressure method, has been investigated by magnetization and Mössbauer spectroscopy studies (MS) in the temperature range 4.2 K to 300 K. The ferromagnetic ordering temperature T C obtained is 272(2) K. Isothermal magnetization curves have been measured at various temperatures, from which the saturation moments ( M sat) have been deduced. The 57Fe MS spectra display standard six-line patterns with an isomer shift typical of Fe3 + and a very small quadrupole splitting (QS = 0.14(1) mm/s above T C). The magnetic hyperfine field at 4.2 K is 276(1) kOe. The temperature dependencies of the iron hyperfine field and M sat (1.83 µ B at 5 K) are almost identical. This shows that the Fe3 + is replacing Co4 + , both of the same electronic configuration. They also interact similarly, namely the Fe–Co exchange is almost identical to the Co–Co exchange. [ABSTRACT FROM AUTHOR]

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]

Abstract: We report properties of the Zn-substituted polycrystalline superconductors BaFe1.87− x Zn x Co0.13As2 (x =0, 0.04, 0.06 and 0.08) prepared at ambient pressure condition. Electrical conductivity and magnetization measurements revealed that the superconductivity is suppressed by at most 2% substitution of Zn, which shows typical behavior of an anisotropically gaped superconductivity rather than an isotropically gaped superconductivity. With increasing the amount of Zn, weak change in superconductivity was observed. It is likely impossible to obtain BaFe1.87− x Zn x Co0.13As2 crystals with x >0.04 at ambient pressure condition. On the basis of the structural and the physical properties of the present system, we discuss a possible mechanism of the superconducting pairing. [Copyright &y& Elsevier]