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Flux Pinning Mechanism In Bafe1.9ni0.1as2 Single Crystals: Evidence For Fluctuation In Mean Free Path Induced Pinning, M Shahbazi-Manshadi, X L Wang, K Y Choi, S X. Dou
Flux Pinning Mechanism In Bafe1.9ni0.1as2 Single Crystals: Evidence For Fluctuation In Mean Free Path Induced Pinning, M Shahbazi-Manshadi, X L Wang, K Y Choi, S X. Dou
Shi Xue Dou
The flux pinning mechanism of BaFe1.9Ni0.1As2 superconducting crystals have been investigated systematically by magnetic measurements up to 13 T at various temperatures. The field dependence of the critical current density, Jc, was analysed within the collective pinning model. A remarkably good agreement between the experimental results and theoretical dl pinning curve is obtained, which indicates that pinning in BaFe1.9Ni0.1As2 crystal originates from spatial variation of the mean free path. Moreover, the normalized pinning force density, Fp, curves versus h1/4B/Birr (Birr is the irreversibility field) were scaled using the Dew-Hughes model. Analysis suggests that point pinning alone cannot explain the observed …
The Flux Pinning Mechanism, And Electrical And Magnetic Anisotropy In Fe1.04te0.6se0.4 Superconducting Single Crystal, Mahboobeh Shahbazi-Manshadi, Xiaolin Wang, S X. Dou, H Fang, C T. Lin
The Flux Pinning Mechanism, And Electrical And Magnetic Anisotropy In Fe1.04te0.6se0.4 Superconducting Single Crystal, Mahboobeh Shahbazi-Manshadi, Xiaolin Wang, S X. Dou, H Fang, C T. Lin
Shi Xue Dou
The temperature and magnetic field dependences of the magnetization and critical current density of Fe1.04Te0.6Se0.4 single crystals have been investigated, and the flux pinning mechanism has been analysed. The normalized pinning force (fp Fp/F p,max) vs. h(H/Hirr) curves, are scaled using the Dew-Hughes theory, f(h) ≈ hp(1 - h)q with p 1.35 and q 3.06. The angular dependence of the resistivity under different magnetic fields shows a dip-like structure, below the superconducting transition temperature. The anisotropic value of 2 was obtained using Ginzburg-Landau theory.
Flux Distribution In Fe-Based Superconducting Materials By Magneto-Optical Imaging, Zhi Wei Lin, Jian Guo Zhu, You Guang Guo, Xiaolin Wang, S X. Dou, Tom H. Johansen, Xun Shi, K Y. Choi
Flux Distribution In Fe-Based Superconducting Materials By Magneto-Optical Imaging, Zhi Wei Lin, Jian Guo Zhu, You Guang Guo, Xiaolin Wang, S X. Dou, Tom H. Johansen, Xun Shi, K Y. Choi
Shi Xue Dou
"This paper presents the magnetic flux distributions in Fe-based superconducting materials including single crystal of Ba(Fe1.9Ni0.1)As2 and Ba(Fe1.8Co0.2)As2, as well as polycrystalline SmFeO0.75F0.2As by means of magneto-optical imaging (MOI) technique. The single crystals were grown out of FeAs flux while polycrystalline sample was grown by hot-press. A MOI film with in-plan magnetization was used to visualize flux distributions at the sample surface. A series of magneto-optical images was taken when the samples were zero-field cooled and field cooled. The flux behavior, including penetration into and expelling from the samples, as well as pinning properties were studied. When external fields increase, …
Reduction Of Superconducting Transition Temperature And Flux Pinning In Al And C Codoped Mgb2 With Insight From First-Principles Calculations, Aihua Li, Xiaolin Wang, S X. Dou, Qiwen Yao, Zhenxiang Cheng, Saeid Soltanian, J M. Yoo, P Munroe
Reduction Of Superconducting Transition Temperature And Flux Pinning In Al And C Codoped Mgb2 With Insight From First-Principles Calculations, Aihua Li, Xiaolin Wang, S X. Dou, Qiwen Yao, Zhenxiang Cheng, Saeid Soltanian, J M. Yoo, P Munroe
Shi Xue Dou
We report for the first time the Al and C codoping effect on the structures and superconductivity in MgB2. It was found that both the lattice parameters and the Tc decreased monotonically with increasing doping level of both Al and C. The Tc dropped to 27.5 and 7 K for x=0.2 and for x =0.4, respectively. The reduction of Tc for the codoping was found to be quicker than for individual Al doping and slower than for individual C doping at the same doping levels. First-principles calculations indicated that the observed decrease in Tc …
Flux Dynamics In (Y, Nd)1ba2cu3o7 Superconductors, A S Mahmoud, Josip Horvat, S X. Dou
Flux Dynamics In (Y, Nd)1ba2cu3o7 Superconductors, A S Mahmoud, Josip Horvat, S X. Dou
Shi Xue Dou
The vortex dynamics of (Y, Nd)Ba2Cu3O7−δ ((Y, Nd)123) superconductors have been studied using magnetic relaxation measurements obtained at different sweep rates. The temperature dependence of the dynamic relaxation rate (Q) is found to be not vanishing at T = 0 K, and also showed well developed maxima becoming broader and tending to move to higher temperatures with decreasing magnetic field. At temperatures close to the critical temperature (T c ), Q(T) showed well-developed minima becoming deeper and tending to move to lower temperatures with increasing field. These minima appeared to occur approximately at the same reduced temperature position [ T/T …
Upper Critical Field And Thermally Activated Flux Flow In Lafeaso1-Xfx, Mahboobeh Shahbazi, Xiaolin Wang, C Shekhar, O N. Srivastava, Z W. Lin, J G. Zhu, S. X. Dou
Upper Critical Field And Thermally Activated Flux Flow In Lafeaso1-Xfx, Mahboobeh Shahbazi, Xiaolin Wang, C Shekhar, O N. Srivastava, Z W. Lin, J G. Zhu, S. X. Dou
Shi Xue Dou
The magneto-resistance, critical current density, Jc, upper critical field, Hc2, and flux pinning properties of LaFeAsO1−xFx superconductors were investigated systematically by magnetic and magneto-transport measurements in the fields up to 13 T over a temperature range of 5–35 K. It was found that the Hc2 increased with increasing fluorine concentration up to x ≤ 0.15, while with higher fluorine doping, Hc2 decreased. A peak effect in the Jc as a function of field was observed at T Uo, scales as Uo/kB ∝ B−n with n = 0.13 for B n =− 0.68 for B > 1 T for LaFeAsO0.85F0.15.
Stress/Strain Induced Flux Pinning In Highly Dense Mgb2 Bulks, Rong Zeng, S X. Dou, Lin Lu, Wenxian Li, Chung-Kiak Poh, Jung Ho Kim, Josip Horvat, Dongqi Shi, Jianli Wang, Paul G. Munroe, X. F. Wang, Rongkun Zheng, S. P. Ringer, M Rindfleisch, Mike Tomsic
Stress/Strain Induced Flux Pinning In Highly Dense Mgb2 Bulks, Rong Zeng, S X. Dou, Lin Lu, Wenxian Li, Chung-Kiak Poh, Jung Ho Kim, Josip Horvat, Dongqi Shi, Jianli Wang, Paul G. Munroe, X. F. Wang, Rongkun Zheng, S. P. Ringer, M Rindfleisch, Mike Tomsic
Shi Xue Dou
We have systematically studied the flux pinning behavior of MgB2 bulks synthesized by direct diffusion of Mg into pressed pellets of high purity crystalline B powder, with and without mixing with C and SiC nanoparticles, at a reaction temperature of 850degC for 10 hrs. All of the samples showed very high purity and high density, but their microstructure and flux pinning behavior showed significant differences. It was found that the pure MgB2 agrees with the deltaTc pinning model, nano-C doped MgB2 agrees with the deltal pinning model, while the SiC+MgB2 composite agrees with the deltaepsiv pinning model (stress/strain field pinning), …
Very Strong Intrinsic Flux Pinning And Vortex Avalanches In (Ba, K)Fe2as2 Superconducting Single Crystals, Xiaolin Wang, Shaban R. Ghorbani, Sung-Ik Lee, S X. Dou, C T Lin, T H. Johansen, K.H Muller, Zhenxiang Cheng, Germanas Peleckis, M Shabazi, A.J Qviller, V Yurchenko, G.L Sun, D.L Sun
Very Strong Intrinsic Flux Pinning And Vortex Avalanches In (Ba, K)Fe2as2 Superconducting Single Crystals, Xiaolin Wang, Shaban R. Ghorbani, Sung-Ik Lee, S X. Dou, C T Lin, T H. Johansen, K.H Muller, Zhenxiang Cheng, Germanas Peleckis, M Shabazi, A.J Qviller, V Yurchenko, G.L Sun, D.L Sun
Shi Xue Dou
We report that the (Ba,K)Fe2As2 crystal with Tc=32 K shows a pinning potential, U0, as high as 104 K, with U0 showing very little field dependence. The (Ba,K)Fe2As2 single crystals become isotropic at low temperatures and high magnetic fields, resulting in a very rigid vortex lattice, even in fields very close to Hc2. The isotropic rigid vortices observed in the two-dimensional (2D) (Ba,K)Fe2As2 distinguish this compound from 2D high-Tc cuprate superconductors with 2D vortices. The vortex avalanches were also observed at low temperatures in the (Ba,K)Fe2As2 crystal. It is proposed that it is the K substitution that induces both almost …
Flux Pinning And Vortex Transitions In Doped Bafe2as2 Single Crystals, S R. Ghorbani, X L. Wang, M Shabazi, S X. Dou, K Y. Choi, C T. Lin
Flux Pinning And Vortex Transitions In Doped Bafe2as2 Single Crystals, S R. Ghorbani, X L. Wang, M Shabazi, S X. Dou, K Y. Choi, C T. Lin
Shi Xue Dou
The vortex liquid-to-glass transition has been studied in Ba0.72K0.28Fe2As2 (BaK-122), Ba(Fe0.91Co0.09)2As2(BaCo-122), and Ba(Fe0.95Ni0.05)2As2(BaNi-122) single crystal with superconducting transition temperature, Tc=31.7, 17.3, and 18 K, respectively, by magnetoresistance measurements. For temperatures below Tc, the resistivity curves were measured in magnetic fields within the range of 0≤B≤13 T, and the pinning potential was scaled according to a modified model for vortex liquid resistivity. Good scaling of the resistivity q(B, T) and the effective pinning energy U0(B,T) were obtained. The vortex state is three-dimensional at temperatures lower than a characteristic temperature T*. The vortex phase diagram was determined based on the evolution of …
Kinetic Roughening Of Magnetic Flux Penetration In Mgb2 Thin Films, Andrea Lucarelli, Stephanie Hummert, Andrea Chaney, Gunter Lupke, Brian Moeckly, Yue Zhao, S X. Dou
Kinetic Roughening Of Magnetic Flux Penetration In Mgb2 Thin Films, Andrea Lucarelli, Stephanie Hummert, Andrea Chaney, Gunter Lupke, Brian Moeckly, Yue Zhao, S X. Dou
Shi Xue Dou
Time-resolved magneto-optical studies are performed on MgB2 thin film samples grown by in situ pulsed laser deposition and in situ reactive deposition technique. The latter reveal dendritic avalanche-free flux penetration. The kinetic roughening of magnetic flux penetration is studied for applied ac current. Dynamic scaling laws determined for both static field and ac current are consistent with the directed percolation depinning model, placing the vortex dynamics in MgB2 in the same universality class as YBCO and Nb.
Strong Competition Between The Delta L And Delta T-C Flux Pinning Mechanisms In Mgb2 Doped With Carbon Containing Compounds, Shaban R. Ghorbani, Xiaolin Wang, Md S. Hossain, Qiwen Yao, S X. Dou, Sung-Ik Lee, K C. Chung, Y K. Kim
Strong Competition Between The Delta L And Delta T-C Flux Pinning Mechanisms In Mgb2 Doped With Carbon Containing Compounds, Shaban R. Ghorbani, Xiaolin Wang, Md S. Hossain, Qiwen Yao, S X. Dou, Sung-Ik Lee, K C. Chung, Y K. Kim
Shi Xue Dou
The transport and magnetic properties of 10 wt % malic acid and 5 wt % nanocarbon doped MgB2 have been studied by measuring the resistivity (p), critical current density (jc), connectivity factor (AF), irreversibility field (Hirr), and upper critical field (Hc2). The pinning mechanisms are studied in terms of the collective pinning model. It was found that both mean free path (δl) and critical temperature (δTc) pinning mechanisms coexist in both doped MgB2. For both the malic acid and nanocarbon doped samples, the temperature dependence of the crossover field, which separates the single vortex and the small bundle pinning regime, …
Dynamics Of Flux-Line Bundles And Voltage-Current Characteristics In A Ba(K)Fe2as2 Single Crystal, K H. Muller, S K. H Lam, Xiaolin Wang, S X. Dou
Dynamics Of Flux-Line Bundles And Voltage-Current Characteristics In A Ba(K)Fe2as2 Single Crystal, K H. Muller, S K. H Lam, Xiaolin Wang, S X. Dou
Shi Xue Dou
Understanding the flux-line dynamics in layered superconductors is of utmost importance for many superconductor applications, yet extracting from measurements the relevant parameters remains a major challenge. Here we report on measurements and theoretical model calculations of voltage-current (V-I) characteristics of a superconducting Ba0.72K0.28Fe2As2 single crystal slightly below its transition temperature in perpendicular magnetic fields between 0.01 and 7 T. We propose a model that describes the flux-line dynamics above, as well as below, the depinning current. The model fits the experimental V-I characteristics remarkably well and is used to extract from the data the field dependence of (a) the depinning …
Flux-Pinning Mechanism In Silicone-Oil Doped Mgb2: Evidence For Charge-Carrier Mean Free Path Fluctuation Pinning, Shaban R. Ghorbani, Xiaolin Wang, S X. Dou, Sung-Ik Lee, Md S. Hossain
Flux-Pinning Mechanism In Silicone-Oil Doped Mgb2: Evidence For Charge-Carrier Mean Free Path Fluctuation Pinning, Shaban R. Ghorbani, Xiaolin Wang, S X. Dou, Sung-Ik Lee, Md S. Hossain
Shi Xue Dou
Flux-pinning mechanism of MgB2 doped with 10 wt % silicone-oil sintered at low and high temperatures has been investigated by magnetic measurements. The field dependence of the critical current density, jc(B), was analysed within the collective pinning model. A crossover field, Bsb, from the single vortex to the small vortex bundle-pinning regime was observed. For both types of sintered samples, the temperature dependence of Bsb(T) at low temperature is in good agreement with the δl pinning mechanism, i.e., pinning associated with charge-carrier mean free path fluctuation. At temperatures close to the critical temperature, however, there is evidence for δTc pinning, …
Flux Pinning Of Stress Induced Magnetic Inhomogeneity In The Bilayers Of Yba2cu3o7-Δ/La0.67sr0.33mno3-Δ, S X. Dou, Rong Zeng, Y M. Lu, L Peng, B Gao, Z Y. Liu, F Fan, C B. Cai, C Z. Chen
Flux Pinning Of Stress Induced Magnetic Inhomogeneity In The Bilayers Of Yba2cu3o7-Δ/La0.67sr0.33mno3-Δ, S X. Dou, Rong Zeng, Y M. Lu, L Peng, B Gao, Z Y. Liu, F Fan, C B. Cai, C Z. Chen
Shi Xue Dou
Elaborately designed bilayers consisting of epitaxial YBa2Cu3O7-δ (YBCO) and La0.67Sr0.33MnO3-δ (LSMO) films were fabricated by pulsed laser deposition with respect to the investigation into magnetic-dependent vortex pinning effect. The improvement in the critical current density and a pronounced upward shift in the superconducting irreversibility line based on magnetotransport measurements are observed when compared to the pure YBCO film, suggesting the enhancement in flux pinning in the studied bilayer. It is believed that the improved flux pinning for YBCO arises from the magnetic inhomogeneity of the underlying LSMO. Magnetization measurements show a nonuniform magnetic state in the LSMO film, most probably …