Nonlinear microwave response of MgB2

Dahm, Thomas; Scalapino, D. J.

doi:10.1063/1.1815067

Cited by 31 publications

(37 citation statements)

References 11 publications

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“…Absolute values of λ in MgB 2 measured with various techniques range from 40 nm to 210 nm. [36][37][38][39][40][41][42] The large variation of λ in MgB 2 may be due to inclusion of impurities, such as C, N, and Al, which replace either Mg or B and significantly affect the electronic structure of the system due to the two-band nature of MgB 2 . The origin of the impurities-induced large value of λ and its temperature dependence obtained from the Meissner response curves in the MgB 2 film taken at different temperatures (not shown) will be described elsewhere.…”

Section: A Mfm Measurement In the Nb Filmmentioning

confidence: 99%

Direct measurement of the magnetic penetration depth by magnetic force microscopy

Kim

Civale

Nazaretski

et al. 2012

Supercond. Sci. Technol.

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We present an experimental approach using magnetic force microscopy for measurements of the absolute value of the magnetic penetration depth λ in superconductors. λ is obtained in a simple and robust way without introducing any tip modeling procedure via direct comparison of the Meissner response curves for a material of interest to those measured on a reference sample. Using a wellcharacterized Nb film as a reference, we determine the absolute value of λ in a Ba(Fe0.92Co0.08)2As2 single crystal and a MgB2 thin film through a comparative experiment. Our apparatus features simultaneous loading of multiple samples, and allows straightforward measurement of the absolute value of λ in superconducting thin film or single crystal samples.

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Section: A Mfm Measurement In the Nb Filmmentioning

confidence: 99%

Direct measurement of the magnetic penetration depth by magnetic force microscopy

Kim

Civale

Nazaretski

et al. 2012

Supercond. Sci. Technol.

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show abstract

“…When the excitation field approaches the critical field, the mechanism of intrinsic nonlinearity is still similar to the NLME and becomes more significant. For example, around T c , this nonlinearity comes from the backflow of excited quasiparticles in a current-carrying superconductor, which results in an effective decrease of the superfluid density [7,8,18]. A two-band quasiparticle backflow calculation has been applied to the MgB 2 intrinsic nonlinearity.…”

Section: Intrinsic Nonlinearity Of Mgbmentioning

confidence: 99%

“…In addition, due to the presence of the band and band, the intrinsic nonlinear response of MgB 2 at low temperature is large compared to single-gap s-wave superconductors [6,7]. Finally, it has been proposed that MgB 2 has 6 nodes in its energy gap [8].…”

Section: Introductionmentioning

confidence: 99%

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MgB2nonlinear properties investigated under localized high rf magnetic field excitation

Tai

Ghamsari

Tan

et al. 2012

Phys. Rev. ST Accel. Beams

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The high transition temperature and low surface resistance of MgB 2 attracts interest in its potential application in superconducting radio frequency accelerating cavities. However, compared to traditional Nb cavities, the viability of MgB 2 at high rf fields is still open to question. Our approach is to study the nonlinear electrodynamics of the material under localized rf magnetic fields. Because of the presence of the small superconducting gap in the band, the nonlinear response of MgB 2 at low temperature is potentially complicated compared to a single-gap s-wave superconductor such as Nb. Understanding the mechanisms of nonlinearity coming from the two-band structure of MgB 2 , as well as extrinsic sources of nonlinearity, is an urgent requirement. A localized and strong rf magnetic field, created by a magnetic write head, is integrated into our nonlinear-Meissner-effect scanning microwave microscope [T. Tai et al., IEEE Trans. Appl. Supercond. 21, 2615(2011. MgB 2 films with thickness 50 nm, fabricated by a hybrid physical-chemical vapor deposition technique on dielectric substrates, are measured at a fixed location and show a strongly temperature-dependent third harmonic response. We propose that several possible mechanisms are responsible for this nonlinear response.

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“…3,9,10 The reported values of λ range from 40 nm to 200 nm, indicating that λ is strongly affected by inter-and intra-band scattering. [14][15][16][17][18][19][20] In this paper we present measurements of the absolute values of λ(T ), employing low temperature magnetic force microscopy (MFM), and of the angulardependent H c2 (T, θ) performed via electrical transport, in a 500-nm thick MgB 2 film. Our MgB 2 film can be described by the dirty limit two-band Usadel equations.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the magnetic penetration depth of a superconducting MgB2thin film with a large intraband diffusivity

et al. 2012

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We report the temperature dependent magnetic penetration depth λ(T ) and the superconducting critical field Hc2(T ) in a 500-nm MgB2 film. Our analysis of the experimental results takes into account the two gap nature of the superconducting state and indicates larger intraband diffusivity in the three-dimensional (3D) π band compared to that in the two-dimensional (2D) σ band. Direct comparison of our results with those reported previously for single crystals indicates that larger intraband scattering in the 3D π band leads to an increase of λ. We calculated λ and the thermodynamic critical field Hc ≈2000 Oe employing the gap equations for two-band superconductors. Good agreement between the measured and calculated λ value indicates the two independent measurements, such as magnetic force microscopy and transport, provide a venue for investigating superconducting properties in multi-band superconductors.

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Nonlinear microwave response of MgB2

Cited by 31 publications

References 11 publications

Direct measurement of the magnetic penetration depth by magnetic force microscopy

Direct measurement of the magnetic penetration depth by magnetic force microscopy

MgB2nonlinear properties investigated under localized high rf magnetic field excitation

Measurement of the magnetic penetration depth of a superconducting MgB2thin film with a large intraband diffusivity

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