TY - JOUR

T1 - 73Ge-NMR study and ab initio calculations on clathrate compound Ba24Ge100

AU - Kanetake, F.

AU - Harada, A.

AU - Rachi, T.

AU - Nagara, H.

AU - Mukuda, H.

AU - Kusakabe, K.

AU - Kitaoka, Y.

AU - Suzuki, N.

AU - Tanigaki, K.

AU - Itoh, K.

AU - Haller, E. E.

PY - 2008

Y1 - 2008

N2 - Through 73Ge-NMR measurements and ab initio calculations, we have studied electronic properties of a type-III clathrate compound Ba24Ge100. At ambient pressure, the nuclear spin-lattice relaxation rate 1/T1T 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 TS1 = 215K and TS2 = 180K. The constant value of 1/T1T at low temperatures is considerably smaller than the value at temperatures higher than TS1, which implies that the density of states at the Fermi level D(EF) significantly decreases from the high temperature value at ambient pressure. From ab initio calculations on Ba24Ge100 as well as Ba24Si100, we speculate the phase changes of Ba24Ge100 in the relevant region of the T-P plane. Our results of NMR measurements and D(EF) calculations for the P4132 and an R3 structures imply that, at high pressures ∼ 2.8 GPa, there should be increase of D(EF) 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 Tc from 0.24 K (at P = 0) to 3.8 K (at P = 2.7 GPa) observed in Ba24Ge100

AB - Through 73Ge-NMR measurements and ab initio calculations, we have studied electronic properties of a type-III clathrate compound Ba24Ge100. At ambient pressure, the nuclear spin-lattice relaxation rate 1/T1T 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 TS1 = 215K and TS2 = 180K. The constant value of 1/T1T at low temperatures is considerably smaller than the value at temperatures higher than TS1, which implies that the density of states at the Fermi level D(EF) significantly decreases from the high temperature value at ambient pressure. From ab initio calculations on Ba24Ge100 as well as Ba24Si100, we speculate the phase changes of Ba24Ge100 in the relevant region of the T-P plane. Our results of NMR measurements and D(EF) calculations for the P4132 and an R3 structures imply that, at high pressures ∼ 2.8 GPa, there should be increase of D(EF) 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 Tc from 0.24 K (at P = 0) to 3.8 K (at P = 2.7 GPa) observed in Ba24Ge100

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U2 - 10.1088/1742-6596/121/5/052011

DO - 10.1088/1742-6596/121/5/052011

M3 - Conference article

AN - SCOPUS:84881444930

VL - 121

JO - Journal of Physics: Conference Series

JF - Journal of Physics: Conference Series

SN - 1742-6588

IS - PART 5

M1 - 052011

T2 - Joint 21st AIRAPT and 45th EHPRG International Conference on High Pressure Science and Technology

Y2 - 17 September 2007 through 21 September 2007

ER -