Thermoelectric Power of MgB2 Single Crystals Doped with Holes and Electrons

K. Oganisian a, K. Rogacki a, C. Sulkowski a, N.D. Zhigadlo b, S. Katrych b and J. Karpinski b a Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław, Poland b Laboratory for Solid State Physics, ETH, 8093 Zurich, Switzerland

Full Text PDF

Received: 6 11 2007;

The thermoelectric power of MgB2 single crystals, non-substituted, single-substituted with C, and co-substituted with C and Li, was investigated in the temperature range from 10 to 300 K. Both the in-plane (Sab) and the out-of-plane (Sc) thermoelectric powers are positive for non-substituted crystals and both Sab and Sc change a sign for crystals doped with electrons when C is substituted for B in the amount larger than 6 at.%. The substitution of C, which supplies electrons mainly into the σ band, reduces the thermoelectric power anisotropy, most likely by increasing the interband scattering. When Li is additionally co-substituted for Mg, Sab remains unchanged but Sc increases substantially. The Li substitution donates holes into the π band rather than into the σ band and in this way modifies the π band properties, including the possible increase in the intraband scattering.

DOI: 10.12693/APhysPolA.114.191 PACS numbers: 74.25.Fy, 74.70.Ad, 74.62.Dh