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The performance of iron-based superconductors in high magnetic fields plays an important role for their practical application. In this work, we measured the magnetostriction and magnetization of BaFe$_{1.908}$Ni$_{0.092}$As$_{2}$ single…

Superconductivity · Physics 2023-08-22 Minjie Zhang , Jiating Wu , Ke Shi , Langsheng Ling , Wei Tong , Chuanying Xi , Li Pi , J. Wosnitza , Huiqian Luo , Zhaosheng Wang

In 1933, Meissner and Ochsenfeld reported the expulsion of magnetic flux, the diamagnetic Meissner effect, from the interior of superconducting lead. This discovery was crucial in formulating the Bardeen-Cooper-Schrieffer (BCS) theory of…

Magneto-optical imaging of a single crystal of CaFe1.94Co0.06As2, shows anomalous remnant magnetization within Meissner like regions of the superconductor. The unconventional shape of the local magnetization hysteresis loop suggests…

Superconductivity · Physics 2012-12-05 Pabitra Mandal , Gorky Shaw , S. S. Banerjee , Neeraj Kumar , S. K. Dhar , A. Thamizhavel

Implanting fully polarized low energy muons on the nanometer scale beneath the surface of a superconductor in the Meissner state enabled us to probe the evanescent magnetic field profile B(z)(0<z<=200nm measured from the surface). All the…

Superconductivity · Physics 2009-11-11 A. Suter , E. Morenzoni , N. Garifianov , R. Khasanov , E. Kirk , H. Luetkens , T. Prokscha , M. Horisberger

We have measured a paramagnetic Meissner effect in Nb-Al2O3-Nb Josephson junction arrays using a scanning SQUID microscope. The arrays exhibit diamagnetism for some cooling fields and paramagnetism for other cooling fields. The measured…

We report on the realization and characterization of a magnetic microtrap for ultra cold atoms near a straight superconducting Nb wire with circular cross section. The trapped atoms are used to probe the magnetic field outside the…

Atomic Physics · Physics 2009-11-13 D. Cano , B. Kasch , H. Hattermann , R. Kleiner , C. Zimmermann , D. Koelle , J. Fortágh

Conventional superconductors respond to external magnetic fields by generating diamagnetic screening currents. However, theoretical work has shown that one can engineer systems where the screening current is paramagnetic, causing them to…

Superconductivity · Physics 2020-02-05 Jabir Ali Ouassou , Wolfgang Belzig , Jacob Linder

I argue that the conventional BCS-London theory of superconductivity does not explain the most fundamental property of superconductors, the Meissner effect: how is the Meissner current generated, and how is it able to defy Faraday's law?…

Superconductivity · Physics 2010-01-13 J. E. Hirsch

Resistivity and ac magnetic susceptibility measurements on Ba2Sn3Sb6 and SrSn3Sb4 indicate that these Zintl compounds display a transition to a superconducting phase at Tc = 3.9 K. The Meissner effect was observed for Ba2Sn3Sb6 under an…

Superconductivity · Physics 2007-05-23 Laura Deakin , Robert Lam , Frank Marsiglio , Arthur Mar

\begin{abstract} We have studied magnetic properties of water-quenched 5 wt.% (Fe, Ti) particle-doped MgB$_2$ comparing with that of air-cooled one. Generally, grain refinement is achieved by increasing cooling rate, which implies an…

Applied Physics · Physics 2020-06-02 H. B. Lee , G. C. Kim , Hyoungjeen Jeen , Y. C. Kim

An electric current generates a magnetic field, and magnetic fields cannot exist in the interior of type I superconductors. As a consequence of these two facts, electric currents can only flow near the surface of a type I superconducting…

Superconductivity · Physics 2021-08-25 J. E. Hirsch

A long-standing theoretical prediction is that in clean, nodal unconventional superconductors the magnetic penetration depth $\lambda$, at zero temperature, varies linearly with magnetic field. This non-linear Meissner effect is an equally…

We report an unusual enhancement of the magnetic induction in single crystals of the magnetic superconductor RbEuFe$_4$As$_4$ , highlighting the interplay between superconducting and magnetic subsystems in this material. Contrary to the…

We investigate Meissner effect in normal metal/superconductor junctions where the interface is spin-active. We find that orbital magnetic susceptibility of the normal metal shows highly nontrivial behaviors. In particular, the magnetic…

Superconductivity · Physics 2011-06-21 Takehito Yokoyama , Yukio Tanaka , Naoto Nagaosa

We report the observation of the Meissner effect in a rhombohedral graphene superconductor, realized via direct imaging of the static fringe magnetic field. In our few-micron sample, the onset of superconductivity manifests as a diamagnetic…

The nature of superconducting fluctuation effects in the isovalently-substituted iron pnictide BaFe$_2$(As$_{1-x}$P$_x$)$_2$ (x=0.35) is probed through measurements of the magnetization and magnetoconductivity around the superconducting…

Superconductivity · Physics 2015-09-25 A. Ramos-Álvarez , J. Mosqueira , F. Vidal , Ding Hu , Genfu Chen , Huiqian Luo , Shiliang Li

We notice some beautiful geometrical defects found in liquid crystals, and explain them by imposing a constraint. We study the way constraints can occur, and introduce the concept of massive fields. We develop the theory of magnetic field…

Condensed Matter · Physics 2008-02-03 James P. Sethna , Ming Huang

The question of how a metal becoming superconducting expels a magnetic field is addressed. It is argued that the conventional theory of superconductivity has not answered this question despite its obvious importance. We argue that the…

Superconductivity · Physics 2016-02-02 J. E. Hirsch

We investigate the influence of Meissner screening and trapped magnetic flux on magnetization dynamics for a Ni80Fe20 film sandwiched between two thick Nb layers (100 nm) using broadband (5-20 GHz) ferromagnetic resonance (FMR)…

The spontaneous expulsion of applied magnetic field, the Meissner effect, is a defining feature of superconductors; in Type-II superconductors above the lower critical field, this screening takes the form of a lattice of magnetic flux…