Non-resonant microwave absorption(NRMA) studies of superconducting MgB2 at a frequency of 9.43 GHz in the field range -50 Gauss to 5000 Gauss are reported. The NRMA results indicate near absence of intergranular weak links. A linear temperature dependence of the lower critical field H c 1 is observed indicating a non s-wave superconductivity. However, the phase reversal of the NRMA signal which...

Superconductivity is an important area of modern research which has benefited enormously from experiments under high pressure conditions. The focus of this paper will be on three classes of high-temperature superconductors: (1) the new binary compound MgB2, (2) the alkali-doped fullerenes, and (3) the cuprate oxides. We will discuss results from experiment and theory which illustrate the kinds ...

Measurements of the superconducting transition temperatures for Al-doped, Cdoped and neutron-damaged-annealed MgB2 samples under pressure up to ∼ 8 kbar are presented. The dTc/dP values change systematically with the decrease of the ambient pressure Tc in a regular fashion. The evolution of the pressure derivatives can be understood assuming that the change in phonon spectrum is a dominant cont...

We investigate flux flow state in the two-gap superconductor in which two s-wave gaps with different amplitudes exist on two separated Fermi surfaces. The flux flow resistivity is obtained based on the Bardeen-Stephen relation and the result agrees well with anomalous field dependence of the flow resistivity recently observed in the two-gap superconductor MgB2. Some typical properties of the vo...

NATURE | VOL 410 | 15 MARCH 2001 | www.nature.com 345 The onsets of the transitions are all in the vicinity of 36 K, the transition temperature for x ˆ 0:10. There is no bulk superconducting transition for x ˆ 0:3 and x ˆ 0:4. The data are interpreted as indicating that bulk superconductivity in single-phase material is suppressed for x greater than 0.10. The superconducting transitions observe...

We characterize the superconducting state of a phase pure polycrystalline sample of the new layered high-temperature superconductor MgB2 by specific heat measurements in magnetic fields up to 9 Tesla. The characteristic jump at the superconducting transition is observed and compared with the predictions of weak coupling BCS-theory and the α-model. Our analysis shows excellent agreement with the...

The discovery of superconductivity at 39 K in magnesium diboride offers the possibility of a new class of low-cost, high-performance superconducting materials for magnets and electronic applications. This compound has twice the transition temperature of Nb3Sn and four times that of Nb-Ti alloy, and the vital prerequisite of strongly linked current ̄ow has already been demonstrated. One possible ...

The discovery of superconductivity in magnesium diboride (MgB2: 39 K, in January 2001) (Nagamatsu et al., 2001) has generated enormous interest and excitement in the superconductivity community and the world in general, but especially among researchers into superconductivity in non-oxide and boron related compounds.