Physical properties of skutterudite-related R3Co4Sn13 (R = La, Ce, Pr, Yb)
H. F. Liu(劉奐甫)1*, C. N. Kuo(郭家農)1,2, C. S. Lue(呂欽山)1,2, Y. K. Kuo(郭永綱)3
1Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
2Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
3Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan
* presenting author:劉奐甫,
We report a systematic study of ternary stannides of R3Co4Sn13 (R = La, Ce, Pr, Yb) by means of the specific heat, 59Co and 119Sn nuclear magnetic resonance (NMR) measurements. Distinctive phenomena associated with the structural phase transition have been identified for La3Co4Sn13, Ce3Co4Sn13 and Pr3Co4Sn13 at T* ~ 160 K, ~155 K and ~ 130 K, respectively. For those materials, relative weak 59Co quadrupole splittings are consistently found below T*, implying that the electrical field gradient (EFG) sensed by the Co site decreases undergoing this phase transition. Such an observation could be attributed to the local distortion of the Sn(2) atom from its initial position below T* which consequently leads to significant modification of the electronic structures around the Fermi surfaces. We also obtained a resolved 119Sn NMR spectrum on Ce3Co4Sn13, revealing that the 119Sn NMR line shape of Sn(2) becomes broaden and the peak feature smears below T*. In addition, the variation of 119Sn NMR Knight shift versus magnetic susceptibility indicates an enhancement on the hyperfine coupling constant on Sn(2) across the phase transition. For Yb3Co4Sn13, however, the specific heat and NMR results show the absence of the structural-related phase transition. The 59Co NMR Knight shift and spin-lattice relaxation rate 1/T1 clearly indicate that Yb3Co4Sn13 is a Pauli-type paramagnet. From the Korringa relation (constant T1T), we thus estimated Co 3d Fermi-level density of states Nd(EF) ~ 3.95 states/eV f.u. for this compound.

Keywords: Rare earth metals and alloys, Electron density of states and band structure of crystalline solids, Charge-density-wave systems, Nuclear magnetic resonance and relaxation