Magnetization and microwave study of superconducting<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">MgB</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Dulčić, A.; Paar, Dalibor; Požek, Miroslav; Williams, G. V. M.; Krämer, Steffen; Jung, C. U.; Park, Min-Seok; Lee, Sung‐Ik

doi:10.1103/physrevb.66.014505

Cited by 19 publications

(7 citation statements)

References 53 publications

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“…(1.22). This is an indication, in agreement with previous findings [143], of the collective nature of the pinning forces in this material. This conclusion is also supported by the low temperatures collapsing of all curves ν 0 (b), with b = B/B c2 (T ).…”

Section: Mgbsupporting

confidence: 93%

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Mixed-State Microwave Response in Superconducting Cuprates

et al. 2006

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We investigate the physics of the microwave response in YBa 2 Cu 3 O 7−δ , SmBa 2 Cu 3 O 7−δ and MgB 2 in the vortex state. We first recall the theoretical basics of vortex-state microwave response in the London limit. We then present a wide set of measurements of the field, temperature, and frequency dependences of the vortex state microwave complex resistivity in superconducting thin films, measured by a resonant cavity and by sweptfrequency Corbino disk. The combination of these techniques allows for a comprehensive description of the microwave response in the vortex state in these innovative superconductors. In all materials investigated we show that flux motion alone cannot take into account all the observed experimental features, neither in the frequency nor in the field dependence. The discrepancy can be resolved by considering the (usually neglected) contribution of quasiparticles to the response in the vortex state. The peculiar, albeit different, physics of the superconducting materials here considered, namely two-band superconductivity in MgB 2 and superconducting gap with lines of nodes in cuprates, give rise to a substantially increased contribution of quasiparticles to the field-dependent microwave response. With careful combined analysis of the data it is possible to extract or infer many interesting quantities related to the vortex state, such as the temperature-dependent characteristic vortex frequency and vortex viscosity, the field dependence of the quasiparticle density, the temperature dependence of the σ-band superfluid density in MgB 2

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Section: Mgbsupporting

confidence: 93%

“…We remark that this is a nontrivial result: previous analysis have never been able to describe the microwave data using the same parameters obtained from low frequency measurements. In particular, the upper critical field was found to be field dependent [143] or anomalous field dependencies for the vortex viscosity were invoked [76].…”

Section: Mgbmentioning

confidence: 99%

Mixed-State Microwave Response in Superconducting Cuprates

et al. 2006

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“…δ v (ω, B, T ) depends on the relative magnitude of the viscous and restoring-pinning forces through the depinning frequency [29]. Since we are analyzing the results in a restrict range of temperature near T c , and considering the values of the depinning frequency reported in the literature for MgB 2 [10,30], it is reasonable to assume that the vortex motion at our working frequency is ruled by the viscous drag force, i.e. vortices move in the flux-flow regime.…”

Section: The Modelmentioning

confidence: 99%

“…Studies reported in the literature on the field-induced variations of R s in MgB 2 have highlighted several anomalies, especially at applied magnetic fields much lower than the upper critical field, among which unusually enhanced field-induced mw losses [8,9,10,11] and a magnetic hysteresis of unconventional shape [11,12,13]. It has been suggested that these anomalies are strictly related to the peculiarities of the fluxon lattice in MgB 2 .…”

Section: Introductionmentioning

confidence: 99%

Field-induced suppression of the pi-band superconductivity and magnetic hysteresis in the microwave surface resistance of MgB_2 at temperatures near T_c

Bonura,

Gallitto,

Vigni

et al. 2009

Preprint

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We report on the magnetic-field-induced variations of the microwave surface resistance, R s , in a polycrystalline MgB 2 sample, at different values of temperature. We have detected a magnetic hysteresis in R s , which exhibits an unexpected plateau on decreasing the DC magnetic field below a certain value. In particular, at temperatures near T c the hysteresis manifests itself only through the presence of the plateau. Although we do not quantitatively justify the anomalous shape of the magnetic hysteresis, we show that the results obtained in the reversible region of the R s (H) curve can be quite well accounted for by supposing that, in this range of magnetic field, the π gap is almost suppressed by the applied field and, consequently, all the π-band charge carriers are quasiparticles. On this hypothesis, we have calculated R s (H) supposing that fluxons assume a conventional (single core) structure and the flux dynamics can be described in the framework of conventional models. From the fitting of the experimental results, we determine the values of H π c2 (T ) at temperatures near T c . In our opinion, the most important result of our investigation is that, at least at temperatures near T c , the value of the applied field that separates the reversible and irreversible regions of the R s (H) curves is just H π c2 (T ); a qualitative discussion of the possible reason of this finding is given.

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“…where the exponent n is an indication of the different vortex dynamics. An exponent of n ∼ 1.5 was found for MgB 2 [171] which is due to a collective pinning commonly observed in LTSC. An exponent of n = 1.5 − 2 was found in HTSC Bi To investigate the doping dependent behavior of B irr , one can scale the irreversible field against B c2 (0) as shown in figure 4.20 by the zero temperature…”

Section: Irreversible Field B Irrmentioning

confidence: 79%

Magnetic and electronic properties of iron-based superconducting systems

Sambale¹

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<p>This thesis is motivated by the large variety of high-temperature superconductors that contain iron in the superconducting layer. This number has grown rapidly since the discovery in 2008 of the iron-pnictides (and chalcogenides), where iron and arsenic form the superconducting layer. Also of interest are the iron-cuprate hybrid materials, where one out of three copper atoms is replaced by iron. The aim is to understand the superconducting, magnetic and electronic properties of these materials in respect to their iron content. This thesis describes some of these properties for the iron-pnictide compounds of CeFeAsO₁₋xFx and AFe₂As₂ (A=Ba, Sr), and for the ironcuprate hybrids of FeSr₂YCu₂O₆₊y and FeSr₂Y₂₋xCexCu₂O₁₀₋y. Here it has been found that CeFeAsO₁₋xFx follows a 3D fluctuation conductivity above the superconducting transition and the thermal activation energy is correlated to the critical current density within a two fluid-flux creep model below the superconducting transition. NMR measurements show that there is considerable charge disorder within the superconducting doping region. The AFe₂As₂ show a positive magnetoresistance, which could be interpreted through three-carrier transport. Superconducting samples of SrFe₂As₂ display a large enhancement in the magnetoresistance below the superconducting transition up to 1600 %, which is due to three-carrier transport through metallic and superconducting regions in an inhomogeneous state. The superconducting properties of the iron-cuprate FeSr₂YCu₂O₆₊y in respect to the location of iron was studied under the influence of electron and hole doping and with additional magnetic impurities. FeSr₂Y₂₋xCexCu₂O₁₀₋y shows a disorder induced spin-glass state and strong localization depending on the doping.</p>

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Magnetization and microwave study of superconductingMgB2

Cited by 19 publications

References 53 publications

Mixed-State Microwave Response in Superconducting Cuprates

Mixed-State Microwave Response in Superconducting Cuprates

Field-induced suppression of the pi-band superconductivity and magnetic hysteresis in the microwave surface resistance of MgB_2 at temperatures near T_c

Magnetic and electronic properties of iron-based superconducting systems

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