Related papers: Universal relationship between crystallinity and i…
We report the detailed study of the irreversibility field {\hirr} of single crystals of Mg(B$_{1-x}$C$_{x}$)$_2$ ($x$=0, 2, 3.5, 5 and 7%) in strong magnetic fields of up to 40 T. High sensitive torque measurements revealed that the {\hirr}…
Low resistivity ("clean") MgB2 bulk samples annealed in Mg vapor show an increase in upper critical field Hc2(T) and irreversibility field Hirr(T) by a factor of 2 in both transport and magnetic measurements. The best sample displayed Hirr…
In a study of the influence of ZrB2 additions on the irreversibility field, Birr and the upper critical field Bc2, bulk samples with 7.5 at. % ZrB2 additions were made by a powder milling and compaction technique. These samples were then…
The upper critical field and flux pinning in MgB2 single crystals were investigated. The implications of these properties for technical applications are discussed and compared with transport properties of polycrystalline bulk samples and…
A strong effect of sample size on magnetic Jc(H) was observed for bulk MgB2 when Jc is obtained directly from the critical state model. Thus obtained zero-field Jc (Jc0) decreases strongly with the sample size, attaining a constant value…
Ex-situ Powder-In-Tube MgB2 tapes prepared with ball-milled, undoped powders showed a strong enhancement of the irreversibility field H*, the upper critical field Hc2 and the critical current density Jc(H) together with the suppression of…
Highly dense nanocrystalline MgB_2 bulk superconductors with distinctly improved pinning were prepared by mechanical alloying of Mg and B powders and hot compaction at ambient temperatures. The nanocrystalline samples reveal high critical…
The anisotropy of the critical current density (Jc) and its influence on measurement of irreversibility field (Birr) has been investigated for high quality, in-situ MgB2 strands. Comparison of transport and magnetization measurements has…
Highly dense MgB2 policrystalline bulk materials, obtained by reactive liquid infiltration, have been characterized in their superconducting transport and magnetic properties in magnetic field and in a temperature range of interest for the…
We investigated the effect of nanoscale-C doping on the critical current density Jc and irreversibility field Birr of Fe-sheathed MgB2 tapes prepared by the in-situ powder-in-tube method. The tapes were heat treated at 600-950C for 1 h.…
The upper critical field Hc2(T) of sintered pellets of the recently discovered MgB_2 superconductor was investigated by transport, ac susceptibility and dc magnetization measurements in magnetic fields up to 16 T covering a temperature…
The effect of high magnetic fields on the current carrying properties of both MgB2 bulks and Fe-sheathed tapes was investigated following different thermal sequences. It is found that application of a large magnetic field during processing…
We report the synthesis and variation of superconductivity parameters such as transition temperature Tc, upper critical field Hc, critical current density Jc, irreversibility field Hirr and flux pinning parameter (Fp) for the MgB2-xCx…
Measurements of the critical current density (Jc) by magnetization and the upper critical field (Hc2) by magnetoresistance have been performed for hafnium-doped MgB2. There has been a remarkable enhancement of Jc as compared to that by ion…
The intrinsic properties of MgB$_2$ form the basis for all applications of this superconductor. We wish to emphasize that the application range of polycrystalline MgB$_2$ is limited by the upper critical field H$_{c2}$ and its anisotropy.…
The accurate charge density of MgB2 was observed at room temperature(R.T.) and 15K by the MEM(Maximum Entropy Method)/Rietveld analysis using synchrotron radiation powder data. The obtained charge density clearly revealed the covalent…
Bulk samples of MgB2 were prepared with 5, 10, and 15% wt.% Y2O3 nanoparticles added using a simple solid-state reaction route. Transmission electron microscopy (TEM) showed a fine nanostructure consisting of ~3-5 nm YB4 nanoparticles…
Critical current density was measured at 4.2 K for MgB2 strands with and without SiC additions. In some cases measurements were performed on longer (1 m) samples wound on barrels, and these were compared to magnetic measurements. Most…
We show that the upper critical field in nanometer-sized Nb particles is governed by the changes in the effective Ginzburg-Landau coherence length occurring due to two competing factors: (i) the decrease in the grain size and consequent…
The upper critical field Hc2||c(0) of 85 kOe in Mg(B0.94C0.06)2 single crystals, determined from torque measurements, is more than twice as large as that one of 31 kOe in unsubstituted MgB2. Anisotropy of Hc2 increases from about 3.4 near…