Safeer Hussain

Bio: Safeer Hussain is an academic researcher from Quaid-i-Azam University. The author has contributed to research in topics: Superconductivity & Diamagnetism. The author has an hindex of 2, co-authored 4 publications receiving 15 citations.

Effect of K-doping to the weak link behaviour of (Cu0.5Tl0.5−xKx)Ba2Ca2Cu3O10−δ superconductors

Abstract: A systematic study of the weak link behaviour for (Cu 0.5 Tl 0.5− x K x )Ba 2 Ca 2 Cu 3 O 10− δ ( x = 0, 0.25) superconductors samples has been carried out using electrical resistivity and AC-susceptibility techniques. The K-doped (Cu 0.5 Tl 0.5− x K x )Ba 2 Ca 2 Cu 3 O 10− δ samples were synthesized by solid-state reaction method. In magnetic susceptibility measurements, the real ( χ ′) and imaginary ( χ ″) parts of the magnetic susceptibility of (Cu 0.5 Tl 0.5− x K x )Ba 2 Ca 2 Cu 3 O 10− δ ( x = 0, 0.25) samples were measured as a function of temperature under various DC-magnetic fields up to 172 Oe. It is observed from these studies that the magnitude of the diamagnetism is substantially enhanced by K-doping. The possible reasons for the enhanced magnitude of diamagnetism have been investigated. It is observed from in-field magnetic measurements that the inter-grain coupling is improved with the K-doping. It is concluded from these studies that potassium atoms appearing at the crystal boundaries enhance inter-grain coupling and pinning mechanism in K-doped (Cu 0.5 Tl 0.25 K 0.25 )Ba 2 Ca 2 Cu 3 O 10− δ superconductors.

Enhanced Superconductivity in (Cu0.5Tl0.25Cs0.25)Ba2Ca2Cu3O10−δ by Cs Doping

Abstract: The self doping of carriers in CuO2 planes (accomplished through post annealing in air, N2 and O2 atmospheres in previous studies) is replaced by a more efficient alkali metal dopant such as Cs. The doping of Cs in the Cu0.5Tl0.5Ba2O4−δ charge reservoir of Cu0.5Tl0.5Ba2Ca2Cu3O10−δ superconductors has been found to enhance its superconducting properties. Enhanced superconductivity parameters, such as Tc, Hc and Jc, most likely arise from the enhanced doping efficiency of Cu0.5Tl0.25Cs0.25Ba2O4−δ charge reservoir layer; since the alkali metals are known to lose their outermost “s-orbital” electron, which could be supplied to conducting CuO2 planes. The distance between efficiently doped CuO2 planes is reduced by Be and Mg doping at the Ca Sites. The quantity of diamagnetism and zero resistivity critical temperature [Tc(R=0)] are suppressed by these substitutions. The post-annealing of the Cs doped samples further enhances their superconducting properties; oxygen doping most likely promotes the optimum holes concentration in the superconducting state in the Cs doped samples. These observations have also shown that the free carrier density plays a significant role in the mechanism of superconductivity which was accomplished by synthesizing (Cu0.5Tl0.25Cs0.25)Ba2Ca2Cu3O10−δ superconductors.

Suppression of Anti-ferromagnetism by K Doping in (Cu0.5Tl0.5−xKx)Ba2Ca2Cu3O10−δ Superconductors

Abstract: In the inner CuO2 planes (IP) of (Cu0.5Tl0.5)Ba2 Ca2Cu3O10−δ superconductors the density of the carriers is in the under-doped state which promotes enhancement in the anti-ferromagnetism. Consequently, the critical temperature of the final compound is suppressed. In the present studies, we have enhanced the density of mobile carriers in the inner CuO2 planes by doping K at the charge reservoir layer by preparing (Cu0.5Tl0.5−x K x )Ba2Ca2Cu3O10−δ superconductors. The higher density of mobile carriers increases the Fermi velocity V F, and hence enhances the superconductivity parameters such as T c, H c, and J c. The main objective of these experiments was to suppress the anti-ferromagnetism in the final compound. We have enhanced the inter-plane coupling by partially substituting Be and Mg at the Ca sites. The melting point of the final compounds is significantly reduced with the incorporation of Be and Mg. The incorporation of these elements has been found to facilitate the formation superconductors with higher numbers of CuO2 planes, i.e., (Cu0.5Tl0.5−x K x )Ba2Ca3−y M y Cu4O12−δ .

Enhanced Inter-grain Connectivity in Nano-particles Doped (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ Superconductors

Abstract: Polycrystalline (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ superconductors show strong composition variations at the termination ends of the crystals which compromise over-all superconducting properties of the final compound. These composition variations are one of the root causes of void formation which produces a poor quality material. The better inter-grain coupling suppresses the Josephson losses required for higher transport critical current density (J c ). The lower losses across the inter-grain Josephson junctions are essential for wire and microelectronic applications. We have fixed such inadvertent composition variation in (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ superconductors by doping them with nano-particles of CuO, BaO and CaO2. Nano-particles doped (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ superconductors were synthesized at 860 °C and characterized using X-ray diffraction (XRD), resistivity (ρ), ac-susceptibility (χ), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) measurements. The magnitude of superconductivity is significantly enhanced with the doping of nano-particles. The samples with 15 wt. % addition of CuO nano-particles have even shown textured elongated crystalline with extremely low population of voids.

Dielectric properties of (CuO, CaO2, and BaO)y/CuTl-1223 composites

Abstract: We synthesized (CuO, CaO2, and BaO)y/Cu0.5Tl0.5Ba2Ca2Cu3O10−δ (y = 0, 5%, 10%, 15%) composites by solid-state reaction and characterized them by x-ray diffraction, scanning electron microscopy, dc-resistivity, and Fourier transform infrared spectroscopy. Frequency and temperature dependent dielectric properties, such as real and imaginary parts of the dielectric constant, dielectric loss, and ac-conductivity of these composites were studied by capacitance and conductance measurements as a function of frequency (10 kHz to 10 MHz) and temperature (78 to 300 K). X-ray diffraction analysis reveals that the characteristic behavior of the superconductor phase and the structure of Cu0.5Tl0.5Ba2Ca2Cu3O10−δ are nearly undisturbed by doping with nanoparticles. Scanning electron microscopy images show the improvement in the intergranular linking between the superconducting grains occurring with increasing nanoparticle concentration. Microcracks are healed up with these nanoparticles, and superconducting volume fract...

Fluctuation-induced conductivity analyses of Be-doped (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10-δ superconductors in the critical regime and beyond

Abstract: We have successfully synthesized (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10−δ and (Bi0.25Cu0.25Li0.25Tl0.25)Ba2(Ca1.5Be0.5)Cu3O10−δ samples and studied their excess conductivity analyses (fluctuation-induced conductivity) of resistivity data. The main objective of such analyses is to investigate the influence of Be-substitution on the superconductivity parameters at the microscopic level. The width of the 3D-2D Lawrence-Doniach regime is increased with the doping of Be at the Ca sites. The energy required to break apart the Cooper pairs is increased from 0.03 eV to 0.08 eV in Be-doped samples. Using the Ginzburg-Landau number (NG) and GL equations, the thermodynamic critical magnetic field Bc(0), the lower critical field Bc1(0), the upper critical field Bc2(0), the critical current density Jc(0), and penetration depth λp.d are also calculated from these analyses. The values of critical fields [Bc(0) Bc1(0)], Jc(0), and phase relaxation time τϕ are increased whereas the penetration depth λp.d and κ values are ...

The excess conductivity of (Cu0.5Tl0.5)-1223 superconductor substituted by Ti

Abstract: Superconducting samples of nominal composition of (Cu 05 Tl 05− x Ti x )Ba 2 Ca 2 Cu 3 O 10− δ ( x = 00, 005, 010, 015, 020 and 025) were prepared by a single step solid-state reaction technique at ambient pressure The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and electron dispersive X-ray (EDX) XRD analysis indicated that the volume fraction of (Cu 05 Tl 05 )-1223 increases from 856% to 882% with increasing of x up to 010 The superconducting transition temperature, T c determined from electrical resistivity data, increases from 1229 to 1253 K as x increases from 00 to 010 and then it decreases to 1165 K for x = 025 The excess conductivity analysis of these samples was analyzed with Aslamazov–Larkin (AL) theory Four different regions were clearly appeared as the temperature was lowered, namely short wave (sw), two dimensional (2D), three dimensional (3D) and critical (cr) fluctuations The superconducting parameters were calculated from excess conductivity analysis as a function of Ti substitution The zero temperature coherence length along the c -axis, ξ c (0) and the interlayer spacing, d decrease as x increases up to x = 010 and then they increase with further increase in x All the estimated interlayer coupling values are less than one, confirming the weak coupling between CuO 2 planes and crossover between 3D and 2D regions