Technical Report of ISSP Ser. A: Number 3115

Abstract

Low-temperature physical properties of a polycrystal and a single crystal of CePt2Sn2 are discussed. The low-temperature specific heat, C(T), and the ac magnetic susceptibility, chi(sub ac)(T), were measured for both samples down to 0.15 K and 0.03 K, respectively. The polycrystalline sample showed an antiferromagnetic transition at T(sub N) = 0.8 K. On the other hand, the single crystal did not exhibit a magnetic transition of long range at 0.8 K, instead exhibited a very sharp cusp in chi(sub ac)(T) at 0.38 K and a broad peak in C(T) around 0.45 K. These anomalies of the single crystal are attributed to a spin-glass transition at T(sub sg) = 0.38 K. The present results on the polycrystal and the single crystal suggest that the previously proposed very-heavy-Fermion state is not realized in CePt2Sn2 but a large part of the enhanced C(T)/T is ascribable to these magnetic phase transitions of localized moments of Ce(3+).

CePt2Sn2の多結晶および単結晶の低温物性を検討した。それぞれ0.15度Kと0.03度Kでの両試料について低温比熱C(T)およびac磁化率χac(T)を測定した。多結晶試料は0.8度Kで反強磁性転移を示した。一方、単結晶は0.8度Kでは磁性転移を示さず、しかし0.38度Kでのχac(T)にシャープなカスプを示し、また0.45度KでのC(T)に広いピークを示した。単結晶のこのような異常性は0.38度Kでのスピンガラス転移に帰することができる。多結晶と単結晶の今回の結果は、以前に提案された非常に重いフェルミオン状態がCePt2Sn2には存在しないが、C(T)/Tの増加の大部分はCe(3+)の局所モーメントの磁性相転移に帰することができることを示唆している。