Pressure Effects on polycrystalline of CeAl₂
T. L. Hung1,2*, C. C. Li3, M. N. Ou2, C. M. Lin4, Y. Y. Chen2, M. K. Wu1,2,5
1Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
2Institute of Physics, Academia Sinica, Taipei, Taiwan
3Department of Earth Science, National Cheng Kung University, Tainan, Taiwan
4Department of Applied Science, National Hsinchu Unererversity of Education, Hsinchu, Taiwan
5Department of Physics, National Dong Hua University, Hualien, Taiwan
* presenting author:洪慈蓮,
Quantum critical point could be induced by pressure effect in heavy fermion compounds. Polycrystalline CeAl₂ specimens have been studied by the measurements of magnetic susceptibility, electrical resistivity and heat capacity under hydrostatic pressure up to 2 GPa. Two kinds of high pressure cells were employed for experimental measurements, one is Be-Cu cell for magnetic susceptibility measurements, the other is diamond anvils cell for electrical resistivity and heat capacity measurements. We observed that Neél temperature below 0.6 GPa increased in our measurements. Because Neél temperature is linearly proportional to exchange constant between to magnetic moments, which can be increased by the reduction of lattice constant under pressure. Consequently, Neél temperature decreased between 0.6 and 2 GPa in electrical resistivity measurement because of quantum critical point. The other result reveals the enhancement of Ce ion effective moment by hydrostatic pressure. At ambient pressure the valence of Ce ion is 3.71, it become 3.65 at 0.9 GPa, indicating the pressure effect will help Ce ion tetravalent transformed to trivalent Ce3+.

Keywords: CeAl2, High pressure, Heavy fermion, Qumtumn critical point