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.