Details of the Superconducting Phase Transition in Nb Showing the Paramagnetic Meissner Effect

Půst, L.; Wenger, L. E.; Koblischka, Michael Rudolf

doi:10.1002/(sici)1521-3951(199904)212:2<r13::aid-pssb999913>3.0.co;2-b

Cited by 2 publications

(2 citation statements)

References 8 publications

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“…The normal state resistivity, ρ(300 K), of Nb was ρ ≈ 0.5 µΩ cm, as in [43]. The measurement revealed a T c of 9.15 K and a residual resistivity of ρ 0 = 0.045 µΩ cm extrapolated from the data towards 0 K. It is interesting to compare this T c value obtained by resistance measurements with the very precise SQUID data obtained in [44][45][46], yielding a T c,onset of 9.21 K at a 0 mT applied field and the variation down to T c = 8 K in a 150 mT applied magnetic field. Panel (c) presents the resistance of a Ta wire with l = 90 mm and diameter 0.5 mm.…”

Section: Methodsmentioning

confidence: 65%

Relation between Crystal Structure and Transition Temperature of Superconducting Metals and Alloys

Koblischka

Roth

Koblischka-Veneva

et al. 2020

Metals

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Using the Roeser–Huber equation, which was originally developed for high temperature superconductors (HTSc) (H. Roeser et al., Acta Astronautica 62 (2008) 733), we present a calculation of the superconducting transition temperatures, T c , of some elements with fcc unit cells (Pb, Al), some elements with bcc unit cells (Nb, V), Sn with a tetragonal unit cell and several simple metallic alloys (NbN, NbTi, the A15 compounds and MgB 2 ). All calculations used only the crystallographic information and available data of the electronic configuration of the constituents. The model itself is based on viewing superconductivity as a resonance effect, and the superconducting charge carriers moving through the crystal interact with a typical crystal distance, x. It is found that all calculated T c -data fall within a narrow error margin on a straight line when plotting ( 2 x ) 2 vs. 1 / T c like in the case for HTSc. Furthermore, we discuss the problems when obtaining data for T c from the literature or from experiments, which are needed for comparison with the calculated data. The T c -data presented here agree reasonably well with the literature data.

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Section: Methodsmentioning

confidence: 65%

Relation between Crystal Structure and Transition Temperature of Superconducting Metals and Alloys

Koblischka

Roth

Koblischka-Veneva

et al. 2020

Metals

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“…Considering both the shape and character of MHLs at various temperatures, and also the FC and ZFC curves studied in detail in refs. [25,139,140], we can attribute the component C to the conventional behavior of a type-II superconductor, where induced currents are governed primarily by vortex pinning. The origin of the component P is still not fully understood.…”

Section: Magnetization Loops Close To the Superconducting Transitionmentioning

confidence: 99%

The Paramagnetic Meissner Effect (PME) in Metallic Superconductors

Koblischka

Půst

Chang

et al. 2023

Metals

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The experimental data in the literature concerning the Paramagnetic Meissner Effect (PME) or also called Wohlleben effect are reviewed with the emphasis on the PME exhibited by metallic, s-wave superconductors. The PME was observed in field-cool cooling (FC-C) and field-cool warming (FC-W) m(T)-measurements on Al, Nb, Pb, Ta, in compounds such as, e.g., NbSe2, In-Sn, ZrB12, and others, and also in MgB2, the metallic superconductor with the highest transition temperature. Furthermore, samples with different shapes such as crystals, polycrystals, thin films, bi- and multilayers, nanocomposites, nanowires, mesoscopic objects, and porous materials exhibited the PME. The characteristic features of the PME, found mainly in Nb disks, such as the characteristic temperatures T1 and Tp and the apparative details of the various magnetic measurement techniques applied to observe the PME, are discussed. We also show that PME can be observed with the magnetic field applied parallel and perpendicular to the sample surface, that PME can be removed by abrading the sample surface, and that PME can be introduced or enhanced by irradiation processes. The PME can be observed as well in magnetization loops (MHLs, m(H)) in a narrow temperature window Tp<Tc, which enables the construction of a phase diagram for a superconducting sample exhibiting the PME. We found that the Nb disks still exhibit the PME after more than 20 years, and we present the efforts of magnetic imaging techniques (scanning SQUID microscopy, magneto-optics, diamond nitrogen-vacancy (NV)-center magnetometry, and low-energy muon spin spectroscopy, (LE-μSR)). Various attempts to explain PME behavior are discussed in detail. In particular, magnetic measurements of mesoscopic Al disks brought out important details employing the models of a giant vortex state and flux compression. Thus, we consider these approaches and demagnetization effects as the base to understand the formation of the paramagnetic signals in most of the materials investigated. New developments and novel directions for further experimental and theoretical analysis are also outlined.

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Details of the Superconducting Phase Transition in Nb Showing the Paramagnetic Meissner Effect

Cited by 2 publications

References 8 publications

Relation between Crystal Structure and Transition Temperature of Superconducting Metals and Alloys

Relation between Crystal Structure and Transition Temperature of Superconducting Metals and Alloys

The Paramagnetic Meissner Effect (PME) in Metallic Superconductors

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