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- Critical current (3)
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Articles 1 - 24 of 24
Full-Text Articles in Engineering
Nanoscale-Sic Doping For Enhancing Jc And Hc2 In Superconducting Mgb2, S X. Dou, V. Braccini, Saeid Soltanian, R. Klie, Y. Zhu, S. Li, Xiaolin Wang, D. Larbalestier
Nanoscale-Sic Doping For Enhancing Jc And Hc2 In Superconducting Mgb2, S X. Dou, V. Braccini, Saeid Soltanian, R. Klie, Y. Zhu, S. Li, Xiaolin Wang, D. Larbalestier
Xiaolin Wang
The effect of nanoscale-SiC doping of MgB2 was investigated in comparison with undoped, clean-limit, and Mg-vapor-exposed samples using transport and magnetic measurements. It was found that there are two distinguishable but related mechanisms that control the critical current-density-field JcsHd behavior: increase of upper critical field Hc2 and improvement of flux pinning. There is a clear correlation between the critical temperature Tc, the resistivity r, the residual resistivity ratio RRR=Rs300 Kd /Rs40 Kd, the irreversibility field H*, and the alloying state in the samples. The Hc2 is about the same within the measured field range for both the Mg-vapor-treated and the …
Order-Disorder Transition In Bi2.1sr1.9cacu2o8 + Delta Single Crystals Doped With Fe And Pb, K. K. Uprety, J. Horvat, Xiaolin Wang, M. Ionescu, Hua-Kun Liu, S. X. Dou, E. H. Brandt
Order-Disorder Transition In Bi2.1sr1.9cacu2o8 + Delta Single Crystals Doped With Fe And Pb, K. K. Uprety, J. Horvat, Xiaolin Wang, M. Ionescu, Hua-Kun Liu, S. X. Dou, E. H. Brandt
Xiaolin Wang
The magnetic field Hdis(T) where an order-disorder transition of the vortex lattice in high-Tc superconductors occurs, is investigated by measurements of the magnetization M(H) in Bi2.1Sr1.9CaCu2O8 + delta (Bi2212) single crystals doped with iron and lead. Comparative studies are made of the temperature dependences of the field Hpeak(T), where the second peak occurs in |M(H)|, and the fields Hmin(T), and Hinfl(T) where a minimum and an inflection point occur at the low-field side of this peak. It is proposed that Hdis(T) lies close to Hinfl. In Bi2.1Sr1.9Ca1.0(Cu1–yFey)2O8 + delta single crystals with Fe concentration y = 0, 0.005, 0.016, and …
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Xiaolin Wang
High-quality bulk MgB2 exhibits a structure of voids and agglomeration of crystals on different length scales. Because of this, the superconducting currents percolate between the voids in the ensuing structure. Magnetic measurements reveal that the superconducting currents circulate on at least three different length scales, of ∼1 μm, ∼10 μm, and whole of the sample (∼millimeter). Each of these screenings contributes to the measured irreversible magnetic moment (Δm). The analysis of the field dependence of Δm for samples of subsequently decreasing size showed that the critical current obtained using the simple critical state model is erroneous. This leads to the …
Improvement Of Critical Current In Mgb2 Superconducting Wires By A Ferromagnetic Sheath, J. Horvat, X. L. Wang, Saeid Soltanian, S. X. Dou
Improvement Of Critical Current In Mgb2 Superconducting Wires By A Ferromagnetic Sheath, J. Horvat, X. L. Wang, Saeid Soltanian, S. X. Dou
Xiaolin Wang
Transport critical current (Ic) was measured for Fe-sheathed MgB2 round wires. A critical current density of 5.3 x 10^4 A/cm^2 was obtained at 32K. Strong magnetic shielding by the iron sheath was observed, resulting in a decrease in Ic by only 15% in a field of 0.6T at 32K. In addition to shielding, interaction between the iron sheath and the superconductor resulted in a constant Ic between 0.2 and 0.6T. This was well beyond the maximum field for effective shielding of 0.2T. This effect can be used to substantially improve the field performance of MgB2/Fe wires at fields at least …
Microstructures And Enhancement Of Critical Current Density In Yba/Sub 2/Cu/Sub 3/O/Sub 7/ Thin Films Grown By Pulsed Laser Deposition On Various Single Crystal Substrates Modified By Ag Nano-Dots, Aihua Li, M. Ionescu, Hua-Kun Liu, Tania M. Silver, Xiaolin Wang, S. X. Dou
Microstructures And Enhancement Of Critical Current Density In Yba/Sub 2/Cu/Sub 3/O/Sub 7/ Thin Films Grown By Pulsed Laser Deposition On Various Single Crystal Substrates Modified By Ag Nano-Dots, Aihua Li, M. Ionescu, Hua-Kun Liu, Tania M. Silver, Xiaolin Wang, S. X. Dou
Xiaolin Wang
YBa2Cu3O7 (Y123) thin films were grown by pulsed laser deposition (PLD) on YSZ (100), SrTiO3 (100), and LaAlO3 (100) single crystal substrates. Prior to the film deposition, a discontinuous layer of Ag nano-dots was deposited on the substrates. The Y123 films grown on such surfaces modified with Ag nano-dots were characterized by Atomic Force Microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM), AC susceptibility and DC magnetization. The effects of the density of Ag nano-dots, which was controlled by the numbers of PLD shots, on the microstructures and resultant critical current density Jc have been studied systematically. Results showed …
Thermal Activation And Ac-Field-Induced Discontinuous Domain Jumps In Perovskite La0.7ca0.3mno3, Xiaolin Wang, J. Horvat, Hua-Kun Liu, S. X. Dou
Thermal Activation And Ac-Field-Induced Discontinuous Domain Jumps In Perovskite La0.7ca0.3mno3, Xiaolin Wang, J. Horvat, Hua-Kun Liu, S. X. Dou
Xiaolin Wang
Low-field ac susceptibility was measured on bulk La0.7Ca0.3MnO3 prepared by a partial melting technique. Discontinuous jumps with heights of (1 - 2)105 emu at temperature intervals of 3-5 K were observed in the ac susceptibility. 28 jumps were observed in the temperature range between 4.2 K and the Curie temperature of 250 K, with an ac field amplitude of 1 Oe, a frequency of 117 Hz, and a dc bias field of 5 and 20 Oe. Upon increasing the frequency up to 5000 Hz, the jumps shifted to lower temperature. For a dc bias field of 50 Oe and an …
Growth, Microstructures, And Superconductivity Of Bi2–Xpbxsr2ca1–Ygdycu2o8 + Z Single Crystals, Xiaolin Wang, E. Takayama-Muromachi, Aihua Li, Z. Cheng, S. Keshavarzi, M. J. Qin, S. X. Dou
Growth, Microstructures, And Superconductivity Of Bi2–Xpbxsr2ca1–Ygdycu2o8 + Z Single Crystals, Xiaolin Wang, E. Takayama-Muromachi, Aihua Li, Z. Cheng, S. Keshavarzi, M. J. Qin, S. X. Dou
Xiaolin Wang
Bi2–xPbxSr2Ca1–yGdyCu2O8 + delta (x = 0.34 and y = 0.18, 0.34) crystals were grown by the self-flux method. The crystals have a cleavage thickness of only half unit cell up to two unit cells with Tc only dropping 20 K as y is increased from 0.18 to 0.34 for as-grown crystals. However, Tc increased to almost the same value of about 80 K after annealing in air regardless of the Gd doping levels. The co-doping produced enhanced flux pinning compared to the sole Gd doping. A secondary peak effect presented in crystals with x = 0.34 and y = 0.34 …
Structures, Spin Glass And Spin States In Perovskite Gdmn/Sub X/Co/Sub 1-X/O/Sub 3/ (X /Spl Les/ 0.5), M Mehdi Farhoudi, Xiaolin Wang
Structures, Spin Glass And Spin States In Perovskite Gdmn/Sub X/Co/Sub 1-X/O/Sub 3/ (X /Spl Les/ 0.5), M Mehdi Farhoudi, Xiaolin Wang
Xiaolin Wang
The structures, ferromagnetism, spin glass and spin states of Co and Mn in a polycrystalline ceramic samples of GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x = 0.2, 0.3, 0.4, 0.5) are presented. X-ray diffraction show that all the samples are single phase and crystallize as orthorhombic structures and that the lattice parameters gradually increase with x. Spin glass state and two peak features (corresponding to first order ferromagnetic and second order transition) in dc and ac susceptibility are observed. Curie-Wise fitting on the inverse susceptibility-temperature plots indicates that the valences of Co or Mn changed from 2+ or 4+ to 3+ when …
Transport Critical Current Density In Fe-Sheathed Nano-Sic Doped Mgb/Sub 2/ Wires, S X. Dou, J. Horvat, Saeid Soltanian, Xiaolin Wang, M. J. Qin, S. H. Zhou, Hua-Kun Liu, P. G. Munroe
Transport Critical Current Density In Fe-Sheathed Nano-Sic Doped Mgb/Sub 2/ Wires, S X. Dou, J. Horvat, Saeid Soltanian, Xiaolin Wang, M. J. Qin, S. H. Zhou, Hua-Kun Liu, P. G. Munroe
Xiaolin Wang
The nano-SiC doped MgB/sub 2//Fe wires were fabricated using a powder-in-tube method and an in-situ reaction process. The depression of T/sub c/ with increasing SiC doping level remained rather small due to the counterbalanced effect of Si and C co-doping. The high level SiC co-doping allowed creation of the intra-grain defects and nano-inclusions, which act as effective pinning centers, resulting in a substantial enhancement in the J/sub c/(H) performance. The transport J/sub c/ for all the wires is comparable to the magnetic J/sub c/ at higher fields despite the low density of the samples and percolative nature of current. The …
Superconductivity And Flux Pinning In Y And Heavily Pb Codoped Bi-2212 Single Crystals, Xiaolin Wang, Hua-Kun Liu, S X. Dou, J. Horvat, D. Millikon, G. Heine, W. Lang, H. M. Luo, Shichao Ding
Superconductivity And Flux Pinning In Y And Heavily Pb Codoped Bi-2212 Single Crystals, Xiaolin Wang, Hua-Kun Liu, S X. Dou, J. Horvat, D. Millikon, G. Heine, W. Lang, H. M. Luo, Shichao Ding
Xiaolin Wang
Studies of superconductivity and flux pinning were carried out on (Bi1.64Pb0.36)Sr2Ca1–xYxCu2O8 + y (x = 0, 0.05, 0.11, 0.33) single crystals grown by the self-flux method. X-ray diffraction, transport, and magnetic measurements were performed for purposes of characterization. X-ray analysis revealed that the c lattice parameter systemically decreases as the Y doping level increases. The superconducting transition temperature Tc decreases from 80 to 30 K as x increases. A strong annealing effect on Tc and superconducting volume has been observed. Resistance measurements show that x = 0.33 samples are semiconductive over a wide temperature range between 4.2 and 300 K …
Spectroscopic Measurements Of Zeeman Splitting Of The Density Of States In High Temperature Superconducting Tunneling Junctions, Gustavo A. Alvarez, I. Iguchi, Xiaolin Wang, S. X. Dou, Qiwen Yao
Spectroscopic Measurements Of Zeeman Splitting Of The Density Of States In High Temperature Superconducting Tunneling Junctions, Gustavo A. Alvarez, I. Iguchi, Xiaolin Wang, S. X. Dou, Qiwen Yao
Xiaolin Wang
We report c-axis tunneling spectroscopy investigations in high magnetic fields (I-V characteristics and tunneling conductance dI/dV) of high quality planar junctions fabricated from c-axis oriented NdBa2Cu3O7–delta/PrBa2Cu3O7–delta/NdBa2Cu3O7–delta thin film multilayers. The tunneling conductance in a parallel magnetic field reveals Zeeman splitting of the quasiparticle density of states. In the presence of spin-orbit interactions, our measurements for the tunneling density of states and the tunneling conductance show a spin splitting of gµBH in energy space of the density of states peak. Here the quantity µB is the Bohr magneton, g is the g factor of the electron, and H is the applied …
Dependence Of The Flux-Creep Activation Energy On Current Density And Magnetic Field For The Mgb2 Superconductor, M. J. Qin, Xiaolin Wang, Saeid Soltanian, Aihua Li, Hua-Kun Liu, S. X. Dou
Dependence Of The Flux-Creep Activation Energy On Current Density And Magnetic Field For The Mgb2 Superconductor, M. J. Qin, Xiaolin Wang, Saeid Soltanian, Aihua Li, Hua-Kun Liu, S. X. Dou
Xiaolin Wang
Systematic ac susceptibility measurements have been performed on a MgB2 bulk sample. We demonstrate that the flux creep activation energy is a nonlinear function of the current density U(j)∝j-0.2, indicating a nonlogarithmic relaxation of the current density in this material. The dependence of the activation energy on the magnetic field is determined to be a power law U(B)∝B-1.33, showing a steep decline in the activation energy with the magnetic field, which accounts for the steep drop in the critical current density with magnetic field that is observed in MgB2. The irreversibility field is also found to be rather low, therefore, …
Effect Of Sample Size On Magnetic Jc For Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Xiaolin Wang, S. X. Dou
Effect Of Sample Size On Magnetic Jc For Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Xiaolin Wang, S. X. Dou
Xiaolin Wang
A strong effect of sample size on magnetic Jc(H) was observed for bulk MgB2 when Jc is obtained directly from the critical state model. Thus obtained zero-field Jc (Jc0) decreases strongly with the sample size, attaining a constant value for the samples larger than a few millimetres. On the other hand, the irreversibility field (Hirr) defined at Jc = 100 A/cm2 increases with the sample size. The decrease of Jc0 is described in terms of voids in the bulk MgB2 samples and superconducting screening around the cells of superconducting material between these voids (35 micro-m), because of concentration of the …
Anomalous Magnetization Peak Effect In Spiral-Grown Bi2sr2cacu2oy Crystals, Xiaolin Wang, J. Horvat, Hua-Kun Liu, J. N. Li, S. X. Dou
Anomalous Magnetization Peak Effect In Spiral-Grown Bi2sr2cacu2oy Crystals, Xiaolin Wang, J. Horvat, Hua-Kun Liu, J. N. Li, S. X. Dou
Xiaolin Wang
Magnetic hysteresis loops were measured on spiral-grown Bi2Sr2CaCu2Oy (Bi-2212) crystals. An anomalous peak effect at a magnetic field of 1000–2000 Oe was observed both in high-Tc (86 K) and oxygen underdoped (Tc=76 K) spiral-grown crystals between 20 and 40 K. The peak effect was observed to be stronger than that induced by oxygen vacancies, defect dislocation networks reported in Bi-2212 crystals. Further, the anomalous peak almost completely disappeared after removing growth spiral patterns from the crystal surface. Edge barriers associated with the growth spirals are suggested to be responsible for the strong peak effect for the spiral-grown Bi-2212 crystals and …
Improvement Of Critical Current Density And Thermally Assisted Individual Vortex Depinning In Pulsed-Laser-Deposited Yba2cu3o7–Delta Thin Films On Srtio3 (100) Substrate With Surface Modification By Ag Nanodots, Aihua Li, Hua-Kun Liu, M. Ionescu, Xiaolin Wang, S. X. Dou, E. W. Collings, M. D. Sumption, M. Bhatia, Z. W. Lin, J. G. Zhu
Improvement Of Critical Current Density And Thermally Assisted Individual Vortex Depinning In Pulsed-Laser-Deposited Yba2cu3o7–Delta Thin Films On Srtio3 (100) Substrate With Surface Modification By Ag Nanodots, Aihua Li, Hua-Kun Liu, M. Ionescu, Xiaolin Wang, S. X. Dou, E. W. Collings, M. D. Sumption, M. Bhatia, Z. W. Lin, J. G. Zhu
Xiaolin Wang
YBa2Cu3O7 films were fabricated by pulsed laser deposition on SrTiO3 (100) single-crystal substrates whose surfaces were modified by the introduction of Ag nanodots. The critical current density (Jc) was found to increase with the number of Ag shots. Zero-field magnetic Jc0 at 77 K increased from 8×105 up to 3.5×106 A/cm2 as the number of Ag shots increased from 0 to over 150 times. Microstructure investigations indicated that the crystallinity and the ab alignment gradually improved as the number of Ag nanodots increased. Thermally activated depinning of individual vortices is suggested responsible for a field-independent Jc plateau.
Enhanced Electrical Polarization And Ferromagnetic Moment In A Multiferroic Bifeo3/Bi3.25sm0.75ti2.98v0.02o12 Double-Layered Thin Film, Z. Cheng, Xiaolin Wang, C. V. Kannan, Kiyoshi Ozawa, H. Kimura, T. Nishida, S. Zhang, T. R. Shrout
Enhanced Electrical Polarization And Ferromagnetic Moment In A Multiferroic Bifeo3/Bi3.25sm0.75ti2.98v0.02o12 Double-Layered Thin Film, Z. Cheng, Xiaolin Wang, C. V. Kannan, Kiyoshi Ozawa, H. Kimura, T. Nishida, S. Zhang, T. R. Shrout
Xiaolin Wang
Multiferroic BiFeO3/Bi3.25Sm0.75Ti2.98V0.02O12 double-layered thin films on Pt/Ti/SiO2/Si were fabricated using the pulsed-laser deposition technique. The films showed greatly enhanced ferroelectric and ferromagnetic properties. The values of the remanent polarization (2Pr) and coercive field (Ec) were 71.8 µC/cm2 and 148 kV/cm at a maximum applied voltage of 13 V, respectively. The value of the magnetic moment was found to be 17.5 emu/cm3. The enhancement of the polarization originated from the BiFeO3 with Bi3.25Sm0.75Ti2.98V0.02O12 working as a barrier layer. The enhancement of the magnetization is from the structural distortion of BiFeO3, due to partial epitaxial growth on the bismuth titanate surface.
Magnetic Shielding In Mgb2/Fe Superconducting Wires, J. Horvat, Saeid Soltanian, Xiaolin Wang, S. X. Dou
Magnetic Shielding In Mgb2/Fe Superconducting Wires, J. Horvat, Saeid Soltanian, Xiaolin Wang, S. X. Dou
Xiaolin Wang
Transport critical current (I/sub c/) was measured for MgB/sub 2//Fe round wires, with the magnetic field oriented perpendicular to the wire and parallel to it. Measurements were made on a wire with a pure MgB/sub 2/ core and another wire where the MgB/sub 2/ core was doped with nano-size SiC. This doping strongly improved the vortex pinning in MgB/sub 2/. The field dependence of I/sub c/ was strongly improved due to the presence of the iron sheath. At 30 K, I/sub c/ did not depend on the field for fields between 0.09 and 0.7 T. At lower temperatures, I/sub c/ …
Third Harmonics Due To Surface Barrier In High-Temperature Superconductor, X. B. Xu, L. Zhang, X. Leng, Shichao Ding, Hua-Kun Liu, Xiaolin Wang, S. X. Dou, Z. W. Lin, J. G. Zhu
Third Harmonics Due To Surface Barrier In High-Temperature Superconductor, X. B. Xu, L. Zhang, X. Leng, Shichao Ding, Hua-Kun Liu, Xiaolin Wang, S. X. Dou, Z. W. Lin, J. G. Zhu
Xiaolin Wang
The influence of surface barrier on the third harmonics ac susceptibility (chi3) is studied numerically. The surface barrier is described by a critical current density in surfaces which are higher than the inside one. The model can act as the critical state one, the flux creep one, or the flux flow one when temperature (or field) changes. The numerical results based on the model are more close to the popular experimental data probing the harmonics as a function of temperature (or field). Besides, the surface barrier will lead to new peaks in the real and imaginary parts of the third …
Absence Of Ferromagnetism And Strong Spin-Orbital Coupling In Polycrystalline In And Co Codoped Zn/Sub 1-X/Co/Sub 0.075/In /Sub X/O Oxide, Germanas Peleckis, Xiaolin Wang, S X. Dou
Absence Of Ferromagnetism And Strong Spin-Orbital Coupling In Polycrystalline In And Co Codoped Zn/Sub 1-X/Co/Sub 0.075/In /Sub X/O Oxide, Germanas Peleckis, Xiaolin Wang, S X. Dou
Xiaolin Wang
Polycrystalline samples of In and Co codoped ZnO (Zn1-xInxCo0.075O; 0.010≤x≤0.020) oxide were prepared by solid-state synthesis technique. Phase purity and structure refinement done by means of the Rietveld analysis technique shows that both Co and In substitute properly into Zn positions. In doping, increased bulk conductivity of the samples at room temperature indicates an increase of charge carrier concentration. All samples showed paramagnetic behavior following Curie-Weiss law at close to room temperatures, with short range antiferromagnetic interaction with Θ≈-200 K. Effective magnetic moment (μeff) calculations showed a strong orbital contribution to the value of μeff, increasing with an increase of …
High Temperature Ferromagnetism In Ni-Doped In2o3 And Indium-Tin Oxide, Germanas Peleckis, Xiaolin Wang, S X. Dou
High Temperature Ferromagnetism In Ni-Doped In2o3 And Indium-Tin Oxide, Germanas Peleckis, Xiaolin Wang, S X. Dou
Xiaolin Wang
Observation of high temperature ferromagnetism in Ni-doped In2O3 and indium-tin-oxide (ITO) samples prepared by a solid state synthesis route is reported. Both Ni-doped compounds showed a clear ferromagnetism above 300 K with the magnetic moments of 0.03–0.06µB/Ni and 0.1µB/Ni at 300 and 10 K, respectively. Ni-doped In2O3 samples showed a typical semiconducting behavior with a room temperature resistivity of ρ ~ 2 Ω cm, while Ni-doped ITO samples were metallic with ρ ~2×10–2 Ω cm. Analysis of different conduction mechanisms suggested that variable range hopping model explains our ρ -T data for the Ni-doped In2O3 sample the best.
Quantum Effects In Small-Capacitance High Temperature Superconducting Tunneling Junctions, Gustavo A. Alvarez, I. Iguchi, Xiaolin Wang, S. X. Dou, Qiwen Yao
Quantum Effects In Small-Capacitance High Temperature Superconducting Tunneling Junctions, Gustavo A. Alvarez, I. Iguchi, Xiaolin Wang, S. X. Dou, Qiwen Yao
Xiaolin Wang
We investigated the effects of single electron charging energy in high temperature superconductors. Various phenomena originating from Coulomb blockade were observable in superconducting tunnel junctions. High quality tunneling junctions were fabricated from c-axis oriented NdBa2Cu3O7–delta/PrBa2Cu3O7–delta/NdBa2Cu3O7–delta thin film multilayers by the pulsed laser deposition method. The current-voltage characteristics (CVCs) show a Coulomb gap for Cooper pair tunneling when the charging energy exceeds the Josephson coupling energy. We found a regime in which the CVCs exhibit sharply defined Coulomb steps due to single electron dynamics and nonlinear tunneling rates. From the obtained Coulomb staircase, the tunneling resistance shows a quantum effect: It …
Three-Dimensional Hysteresis Of Soft Magnetic Composite, Z. W. Lin, J. G. Zhu, Y. G. Guo, Xiaolin Wang, S. Y. Ding
Three-Dimensional Hysteresis Of Soft Magnetic Composite, Z. W. Lin, J. G. Zhu, Y. G. Guo, Xiaolin Wang, S. Y. Ding
Xiaolin Wang
Hysteresis phenomenon is one of the important characteristics of soft magnetic materials. A three-dimensional (3D) magnetic property measurement system has been developed. This system can effectively control the locus of the time-varying magnetic flux density vector B and measure the corresponding magnetic field strength vector H in a cubic sample of soft magnetic material. The sample involved in this study is a soft magnetic composite sample made of highly pure iron powder. This paper investigates the B and H loci in 3D space and the power loss when the B loci are controlled to become circles and ellipses lying in …
Absence Of Ferromagnetism And Strong Orbital Coupling In Carrier Rich Zn/Sub 1-X/In/Sub X/Co/Sub 0.075/O, Xiaolin Wang, Germanas Peleckis, S X. Dou
Absence Of Ferromagnetism And Strong Orbital Coupling In Carrier Rich Zn/Sub 1-X/In/Sub X/Co/Sub 0.075/O, Xiaolin Wang, Germanas Peleckis, S X. Dou
Xiaolin Wang
Polycrystalline samples of Zn/sub 1-x/In/sub x/Co/sub 0.075/O (0.010/spl les/x/spl les/0.020) diluted magnetic semiconductors were prepared by the rapid oxalate decomposition technique. Phase purity is analyzed by means of X-ray diffraction technique and structures are refined by Rietveld refinement technique. Bulk conductivity of the polished pellets was measured by two-point probe technique at 295 K. Magnetic properties were analyzed with magnetic property measurement system. Samples show paramagnetic behavior and Curie-Weiss fitting at high temperature range gave effective magnetic moment of Co ions. Magnetization behavior caused by applied magnetic field was also investigated. High itinerant carrier concentration was achieved but no ferromagnetism …
Positive In-Plane And Negative Out-Of-Plane Magnetoresistance In The Overdoped High-Temperature Superconductor Bi2sr2cacu2o8 + X, G. Heine, W. Lang, Xiaolin Wang, S. X. Dou
Positive In-Plane And Negative Out-Of-Plane Magnetoresistance In The Overdoped High-Temperature Superconductor Bi2sr2cacu2o8 + X, G. Heine, W. Lang, Xiaolin Wang, S. X. Dou
Xiaolin Wang
The in-plane and out-of-plane magnetoresistances of moderately overdoped Bi2Sr2CaCu2O8+x single crystals have been studied from Tc+5 K to Tc+100 K with the magnetic field oriented perpendicular and parallel to the current, respectively. The in-plane magnetoresistance is positive, the out-of-plane magnetoresistance negative, and their temperature variations depend on the orientation of the magnetic field. A recent theory for superconducting order parameter fluctuations is extended for the interaction of carrier spins with the magnetic field. The anomalous, anisotropic magnetoresistance can be described well by a unique set of physical parameters, which were found to correspond to estimates from the normal-state transport properties.