Magnetization Relaxation in Superconducting YBa2Cu3O7 Films with Embedded Nanorods and Nanoparticles

Miu, L.; Mele, P.; Ivan, I.; Ionescu, A.; Crisan, A.; Badica, P.; Miu, Dana

doi:10.1007/978-3-662-44479-5_9

Cited by 2 publications

(2 citation statements)

References 62 publications

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“…In order to confirm the value of p, we made m(t) measurements in DC magnetic field, more exactly, we measured the magnetization relaxation rate S=Δln(|m|)/Δln(t) versus temperature T as is shown figure 3. As might be seen for and a plastic creep process similar to nonuniform single vortex creep dominates de flux dynamics [17,18]. In this scenario, it is known that for a magnetic relaxation curve at given H dc and T, U * (J)=U c (J c0 /J) p [10], so the creep exponent p can be obtained from the linear fit of U * versus 1/J in log-log scale which in our case provides p~−1 (see the inset to figure 3).…”

Section: Resultsmentioning

confidence: 86%

Vortex dynamics driven by AC magnetic field in YBCO thin films with complex pinning structures

Ivan¹,

Sandu²,

Crisan³

et al. 2018

Supercond. Sci. Technol.

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We investigated the AC magnetic response of a YBa 2 Cu 3 O 7 film with embedded BaZrO 3 nanorods and Y 2 O 3 nanoparticles at a static magnetic field H dc lower than the matching field H Φ. We proposed a practical formula for the determination of the induced current J during AC susceptibility measurements, which allows us to directly obtain the pinning potential U c from the characteristics of electric field E versus J. We show that the dynamic critical current J d induced at the depinning frequency f d can be experimentally obtained by measuring m′(T) and m″(T) at different frequencies and amplitudes. It was found that the value of f d obtained by extrapolation of J to J d in the PHz domain is much higher than the frequency reported for ordinary YBa 2 Cu 3 O 7 thin films as determined by microwave impedance measurements.AC susceptibility, vortex dynamics, pinning energy, depinning frequency, dynamic critical current, microwave impedance measurements

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Section: Resultsmentioning

confidence: 86%

Vortex dynamics driven by AC magnetic field in YBCO thin films with complex pinning structures

Ivan¹,

Sandu²,

Crisan³

et al. 2018

Supercond. Sci. Technol.

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“…In quantum confined systems, the discrete energy spectra make the geometry dependence of the physical properties of materials prominent, which were negligible at macroscale [5][6][7][8][9]. Quantum size effect is perhaps the best known of the geometric effects appearing at nanoscale [10][11][12][13] and the importance of the energy quantization and a few-level systems has led to the study of quantum heat machines highlighting the essence of this effect [14][15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Spectral properties of size-invariant shape transformation

Aydin¹

2023

Preprint

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Size-invariant shape transformation is a technique of changing the shape of a domain while preserving its sizes under the Lebesgue measure. In quantum confined systems, this transformation leads to so-called quantum shape effects in the physical properties of confined particles associated with the Dirichlet spectrum of the confining medium. Here we show that the geometric couplings between levels generated by the size-invariant shape transformations cause nonuniform scaling in the eigenspectra. In particular, the nonuniform level scaling is characterized by two distinct spectral features: lowering of the first eigenvalue (ground state reduction) and changing of the spectral gaps (energy level splitting or degeneracy formation depending on the symmetries). We explain the ground state reduction by the increase in local breadth (i.e. parts of the domain becoming less confined) that is associated with the sphericity of these local portions of the domain. We accurately quantify the sphericity using two different measures: the radius of the inscribed n-sphere and the Hausdorff distance. Due to Rayleigh-Faber-Krahn inequality, the greater the sphericity, the lower the first eigenvalue. Then, level splitting or degeneracy, depending on the symmetries of the initial configuration, becomes a direct consequence of size-invariance dictating the eigenvalues to have the same asymptotic behavior due to Weyl law. Furthermore, we find that the ground state reduction causes a quantum thermal avalanche which is the underlying reason for the peculiar effect of spontaneous transitions to lower entropy states in systems exhibiting the quantum shape effect. Unusual spectral characteristics of size-preserving transformations can assist in designing confinement geometries that could lead to classically inconceivable quantum thermal machines.

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Magnetization Relaxation in Superconducting YBa2Cu3O7 Films with Embedded Nanorods and Nanoparticles

Cited by 2 publications

References 62 publications

Vortex dynamics driven by AC magnetic field in YBCO thin films with complex pinning structures

Vortex dynamics driven by AC magnetic field in YBCO thin films with complex pinning structures

Spectral properties of size-invariant shape transformation

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