Kijoon H. P. Kim

High Current-Carrying Capability in c-Axis-Oriented Superconducting MgB2 Thin Films

In high-quality c-axis-oriented MgB2 thin films, we observed high critical current densities ( J(c)) of approximately 16 MA/cm(2) at 15 K under self-fields comparable to those of cuprate high-temperature superconductors. The extrapolated value of J(c) at 5 K was estimated to be approximately 40 MA/cm(2). For a magnetic field of 5 T, a J(c) of approximately 0.1 MA/cm(2) was detected at 15 K, suggesting that this compound would be a very promising candidate for practical applications at high temperature and lower power consumption. The vortex-glass phase is considered to be a possible explanation for the observed high current-carrying capability.

Superconducting properties of well-shaped MgB2 single crystals

We report measurements of the transport and the magnetic properties of high-quality, sub-millimeter-sized

Hole carrier in MgB2 characterized by Hall measurements

{\mathrm{MgB}}_{2}

Effect of sintering temperature under high pressure on the superconductivity of MgB2

single crystals with clear hexagonal-plate shapes. The low-field magnetization and the magnetic hysteresis curves show the bulk pinning of these crystals to be very weak. The Debye temperature of

Direct evidence of phase separation in Ge2Sb2Te5 in phase change memory devices

{\ensuremath{\Theta}}_{D}\ensuremath{\sim}1100 \mathrm{K},

Anisotropies of the lower and upper critical fields in MgB2 single crystals

obtained from the zero-field resistance curve, suggests that the normal-state transport properties are dominated by electron-phonon interactions. The resistivity ratio between 40 K and 300 K was about 5, and the upper critical field anisotropy ratio was

Negligible effect of grain boundaries on the supercurrent density in polycrystalline MgB2

3.0\ifmmode\pm\else\textpm\fi{}0.2

Thermoelectric heating of Ge2Sb2Te5 in phase change memory devices

at temperatures around 32 K.

Prominent bulk pinning effect in the MgB 2 superconductor

The longitudinal resistivity (ρxx) and Hall coefficient (RH) were measured for MgB2 sintered under high pressure. We found that RH is positive like cuprate high-Tc superconductors, and decreases as the temperature increases for 40 K <T<300 K. The cotangent of the Hall angle was found to follow a+bT2 behavior from Tc to 300 K. At T=100 K, RH=4.1×10−11 m3/C from which the hole carrier density was determined to be 1.5×1023/cm3. This carrier density is 1–2 orders of magnitude larger than those of Nb3Sn and optimally doped YBa2Cu3Oy superconductors.

Microstructure and pinning properties of hexagonal-disc shaped single crystalline MgB2

We report on the effect of sintering temperature on the superconductivity of MgB2 pellets prepared under a high pressure of 3 GPa. The superconducting properties of the nonheated MgB2 were poor. However, as the sintering temperature increased, the superconducting properties were vastly enhanced, which was demonstrated by the narrow transition width for the resistivity and the low-field magnetization. The observed surface morphology using scanning electron microscopy showed that these changes were closely related to changes in the microscopic level such as the connectivity of the grains.