The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately ...

Superconducting wires are widely used for fabricating magnetic coils in fusion reactors. Superconducting magnet system represents a key determinant of the thermal efficiency and the construction/operating costs of such a reactor. In consideration of the stability of 11B against fast neutron irradiation and its lower induced radioactivation properties, MgB2 superconductor with 11B serving as the...

We report a detailed study of the electronic structure of the MgB2 with different lattice constants by using the full-potential linearized augmented plane wave(FPLAPW) method. It is found that the lattice parameters have great effect on the σ band of Boron. Our results indicate that increasing lattice constant along the c axis will increase the density of states(DOS) at the Fermi level, making ...

The development of the MgB2 manufacturing process to increase current density is an important issue study. In this work, ceramics were manufactured by using solid-state technique. To study influence dry milling on formation and grain size, variations in ball powder weight ratio (BPR) sintering temperature used as control parameters. Magnesium boron with stoichiometric 2:1 was weighed milled for...

Grain morphology and crystallographic texture were investigated by electron microscopy in four different polycrystalline forms of superconducting MgB2. The materials included a hot-pressed sintered MgB2 pellet, a pellet reacted in situ from Mg and B, an in situ reacted MgB2 filament and a pulsed-laser-deposited thin film grown on a single crystalline [111] oriented SrTiO3 substrate. Thick plate...

The recently discovered intermetallic superconductor MgB2 appears to have a highly anisotopic upper critical field with H c2 /H min c2 ≡ γ > 5. In order to determine the temperature dependence of both H c2 and H min c2 we propose a method of extracting the superconducting anisotropy from the magnetization M(H,T ) of randomly oriented powder samples. The method is based on two features in (∂M/∂T...

MgB2 wires, tapes and bulk samples produced within the EU-funded HIPERMAG project have been studied by a combination of X-ray diffraction and electron microscopy. The reaction layers forming at the interface between the ceramic core and Fe or Ni sheaths can be studied with both methods. The complementary techniques enable to study both the microstructure and the formation kinetics of the interf...

We present a study of the effects of non-stoichiometry, boron purity, wire diameter and post-synthesis treatment (etching and Mg distilling) on the temperature dependent resistance and resistivity of sintered MgB2 pellets and wire segments. Whereas the residual resistivity ratio (RRR) varies between RRR ≈ 4 to RRR ≥ 20 for different boron purity, it is only moderately affected by non-stoichiome...

An overview of the theory of the upper critical field in dirty two-gap superconductors, with a particular emphasis on MgB2 is given. We focus here on the maximum Hc2 which may be achieved by increasing intraband scattering, and on the limitations imposed by weak interband scattering and paramagnetic effects. In particular, we discuss recent experiments which have demonstrated tenfold increase o...