S. Y. Lee

Hole carrier in MgB2 characterized by Hall measurements

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.

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

Temperature- and magnetic-field-dependent resistivity of MgB2 sintered at high-temperature and high-pressure condition

We report the temperature- and magnetic-field-dependent resistivity of MgB2 sintered at high-temperature and high-pressure condition. The superconducting transition width for the resistivity measurement was about 0.4 K, and the low-field magnetization showed a sharp superconducting transition with a transition width of about 1 K. The resistivity in the normal state roughly followed T2 behavior with smaller residual resistivity ratio (RRR) of 3 over broad temperature region above 100 K rather than reported T3 behavior with larger RRR value of ∼20 in the samples made at lower pressures. Also, the resistivity did not change appreciably with the applied magnetic field, which was different from previous report. These differences were discussed with the microscopic and structural change due to the high-pressure sintering.

Prominent bulk pinning effect in the MgB 2 superconductor

We report the magnetic-field dependence of the irreversible magnetization of the recently discovered binary superconductor

Substitution for Cu in the electron-doped infinite-layer superconductor Sr0.9La0.1CuO2:Ni reduces Tc much faster than Zn

{\mathrm{MgB}}_{2}.

High-pressure synthesis of the homogeneous infinite-layer superconductor Sr0.9La0.1CuO2

For the temperature region of

Synthesis and pinning properties of the infinite-layer superconductor Sr0.9La0.1CuO2

Tl{0.9T}_{c},

Subjective health status and relative factors of old-old elderly of more than 75-year-old -Based on 2011 Korea National Health and Nutrition Examination Survey-

the contribution of the bulk pinning to the magnetization overwhelms that of the surface pinning. This was evident from the fact that the magnetization curves

The effects of Social Capital of old-old elderly of more than 70-year-old on their health-related quality of life

M(H)

Synthesis and characterization of the infinite-layer superconductor Sr0.9La0.1CuO2☆

were well described by the critical-state model without considering the reversible magnetization and the surface-pinning effect. It was also found that the