相关论文: Surface barrier and bulk pinning in MgB$_2$ superc…
Hot Isostatic Pressing was applied to synthesize bulk samples with diameter up to 30 mm starting with Alfa Aesar magnesium diboride powder. HIPing at 2 kbar, 1000 C with cooling under pressure (DMCUP cycle) resulted in a fully dense (or low…
Porous magnesium diboride samples have been prepared by the heat treatment of a pressed mixture of Mg and MgB2 powders. It was found that linked superconducting structure is formed down to the minimum normalized density gamma= d/do= 0.16…
The discovery of superconductivity at 39 K in MgB2[1] raises many issues. One of the central questions is whether this new superconductor resembles a high-temperature-cuprate superconductor or a low-temperature metallic superconductor in…
The distribution of magnetic field in single-phase polycrystalline bulk MgB2 has been measured using a Magneto-Optical (MO) technique for an external magnetic field applied perpendicular to the sample surface. The MO studies indicate that…
The microwave response of three high-density bulk MgB2 samples has been investigated in the linear and nonlinear regimes. The three samples, characterized by different mean size of grains, have been obtained by reactive infiltration of…
By scaling isothermal magnetization data measured at different temperatures in the mixed state of high-Tc superconductors, we show that in some cases the sample magnetization, measured in increasing magnetic field below the irreversibility…
We present scanning tunneling microscopy measurements of the surface of superconducting MgB2 with a critical temperature of 39K. In zero magnetic field the conductance spectra can be analyzed in terms of the standard BCS theory with a…
The magnetic response of type-II superconductors can be irreversible due to two different reasons: vortex pinning and barriers for flux penetration. Even without bulk pinning and in absence of a microscopic Bean-Lingston surface barrier for…
For the first time, magnetization of high-Tc samples with different crystalline structure and its isothermal relaxation is studied at very weak constant fields (H <= 0.1 Oe) for temperatures close to the critical ones. Essential influence…
Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging (MRI). The recent global helium shortage has…
The structural properties of MgB2 superconductors have been analyzed by means of convergent-beam electron diffraction, high-resolution transmission-electron microscopy, and theoretical simulations. The MgB2 crystal has been identified to…
The recent discovery of intermediate-temperature superconductivity (ITC) in MgB2 by Akimitsu et al. and its almost simultaneous explanation in terms of a hole-carrier-based pairing mechanism by Hirsch, has triggered an avalanche of studies…
We present a novel technique for the investigation of local variations of the critical current density in large bulk superconductors. In contrast to the usual Hall probe scanning technique, the sample is not magnetized as a whole before the…
The recently discovered intermetallic superconductor MgB2 appears to have a highly anisotopic upper critical field with Hc2(max)/Hc2(min} = \gamma > 5. In order to determine the temperature dependence of both Hc2(max) and Hc2(min) we…
We review some recent results on the phenomenon of surface superconductivity in the framework of Ginzburg-Landau theory for extreme type-II materials. In particular, we focus on the response of the superconductor to a strong longitudinal…
The interplay of BCS superconductivity and nontrivial band topology is expected to give rise to opportunities for creating topological superconductors, achieved through pairing spin-filtered boundary modes via superconducting proximity…
Muon spin spectroscopy is one of the most powerful tools to investigate the microscopic properties of superconductors. In this manuscript, an overview on some of the main achievements obtained by this technique in the iron-based…
We report $^{11}$B-NMR study on Al-doped MgB$_2$ that addresses a possible mechanism for a high superconducting (SC) transition temperature ($T_c$) of $\sim 40$ K in recently discovered MgB$_2$. The result of nuclear spin lattice relaxation…
We have measured the Raman spectra of polycrystalline MgB$_{2}$ from 25 {\cm} to 1200 {\cm}. When the temperature was decreased below the superconducting transition temperature $T_c$, we observed a superconductivity-induced redistribution…
Magnetisation of superconductors are often measured under isothermal and uniform magnetic fields. Magnetisation measurements in an unrestricted thermodynamic state and in non uniform magnetic fields naturally emerge from permanent magnets…