Year: 2008
Type: conference-paper
Abstract: Through 73 Ge-NMR measurements and ab initio calculations, we have studied electronic properties of a type-III clathrate compound Ba 24 Ge 100 . At ambient pressure, the nuclear spin-lattice relaxation rate 1/ T 1 T has a peak around 200K followed by an activation type decrease with decreasing temperature and it becomes constant at very low temperatures. Near the peak temperature, the successive structural transformations have been observed at T S1 = 215K and T S2 = 180K. The constant value of 1/ T 1 T at low temperatures is considerably smaller than the value at temperatures higher than T S1 , which implies that the density of states at the Fermi level D ( E F ) significantly decreases from the high temperature value at ambient pressure. From ab initio calculations on Ba 24 Ge 100 as well as Ba 24 Si 100 , we speculate the phase changes of Ba 24 Ge 100 in the relevant region of the T - P plane. Our results of NMR measurements and D ( E F ) calculations for the P 4 1 32 and an R 3 structures imply that, at high pressures ∼ 2.8 GPa, there should be increase of D (E F ) from the value at ambient pressure and low temperatures. We conclude that this result is predominantly related with the large enhancement of the superconducting transition temperature T c from 0.24 K (at P = 0) to 3.8 K (at P = 2.7 GPa) observed in Ba 24 Ge 100
Authors: F Kanetake, A Harada, T Rachi, H Nagara, H Mukuda, K Kusakabe, Y Kitaoka, N Suzuki, K Tanigaki, K Itoh, E E Haller
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W2033190849