Heavy fermion ground states in Th_2Zn_<17>-and BaAl_4-type Ce and U ternary intermetallic

Th_2Zn_<17>-和BaAl_4-型Ce、U三元金属间化合物中的重费米子基态

• 批准号: 07454244
• 负责人: KONTANI Masaaki
• 金额: $ 0.32万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07454244/
• 关键词: heavy fermion system; antiferromagnetism; Th_2Zn_<17->tyep Ce_2Cu_xAl_<17-x>; BaAl_4-type CeCuAl_3; NMR; low temperature specific heat; high pressure; high magnetic field; Th_2Zn_<17>Ce_2Cu_xAl_<17-x>; BaAl_4型CeCuAL_3; 圧力; 単結晶; 磁場中比熱

Th_2Zn_<17>-type Ce- and U- ternary intermetallic compounds : Ce_2Cu_xAl_<17-x> (6.75*x*8.25) was found to crystallize in the Th_2Zn_<17>-type structure. The low temperature and high magnetic fields specific heats, magnetic susceptibility and electrical resistivity indicated that the Kondo temperature T_K increases with x and the system for all the compositions belong to non-magnetic super-heavy-fermion system with giant electronic specific coefficients gamma (=C/T) over 1.5 J/K^2mol-Ce. The f-electron contributions were estimated using the results of Y_2Cu_xAl_<17-x> as a non-magnetic reference. We also succeeded in finding new heavy fermion materials in U-system, U_2Cu_xAl_<17-x> (8*x*11) and U_2Cu_xGa_<17-x> (8*x*12). The single crystals were also obtained. The specific heat down to 0.2K and up to 5.2 T revealed that the extremely large C/T values of -1 J/K^2 mol-U are proportional to -logT at temperatures below 1 K and are little affected by magnetic fields up to 5.2 T,which behavi … More ors are quite contrary to Ce_2Cu_xAl_<17-x> system. These systems showed short range magnetic orders like spin-glasses as well as the non-Fermi-liquid behavior.BaAl_4-type Ce ternary compounds : In addition to macroscopic measurements of CeCuAl_3 single crystals, we performed NMR measurements of ^<63,65>Cu and ^<27>Al for a grain-aligned sample by magnetic fields. From these experiments we clarified that CeCuAl_3 is an antiferromagnets with a Neel temperature of T_N=2.5K and the K vs x plot provided H_<hf> at each Cu and Al site and the 1/T_1 gave important microscopic aspects of f-electron states. The NMR measurements also suggested that CeCuAl_3 crystallizes in the BaNiSn_3 type structure rather than BaAl_4-type. We also succeeded in growing single crystals of CeCuGa_3 with the same crystal structure as CeCuAl_3 and performed the above measurements. We clarified that CeCuGa_3 is an antiferromagnet with T_N=4 K and the first energy splitting DELTA_1 in the crystal field splitting is several tens of degrees, which is much larger than 10K for CeCuAl_3.CeCuAl_3 lies in an interesting regime with competing T_K, RKKY exchange interaction T_<RKKY> and DELTA_1, each other. In order to investigate the effect on pressure against this competition, we developed high pressure NMR and magnetization measurement systems. The NMR measurements in pressures up to 15 kbar revealed that the magnetic properties of CeCuAl_3 are strongly influenced by pressure. With increasing pressure, the value of T_K increases and T_N decreases, and the antiferromangetic state disappeared completely above 10 kbar. The study of CeCu_x (Al, Ga)_<4-x> system are also in progress. Less

th_2zn_ <17> -Type Ce-和U-三元金属间化合物：CE_2CU_XAL_ <17-X>（6.75*X*8.25）在TH_2ZN_ <17> -type结构中结晶。低温和高磁场的特异性热量，磁化率和电抗性表明，随着1.5 j/k^2mol-ce的巨大电子特异性系数gamma（= c/t），近托温度T_K随X随X和所有组合物的系统均均属于非磁性超高铁系统。使用Y_2CU_XAL_ <17-X>作为非磁性参考的结果估算了F-电子贡献。我们还成功地在U-System中找到了新的重费材料，U_2CU_XAL_ <17-X>（8*x*11）和u_2cu_xga_ <17-x>（8*x*12）。还获得了单晶。特定的热量降至0.2K和高达5.2 t，表明-1 j/k^2 mol -u的极大的C/T值与低于1 K的温度与-logt成正比，并且很少受到5.2 t的磁场影响，最多可达5.2 t，而这种行为与CE_2CU_XAL__XAL___XAL_ <17 -X>系统相反。这些系统显示出短范围的磁性顺序，例如旋转玻璃和非纤维液体行为。BAAL_4型CE Ternary化合物：除了对CECUAL_3单晶的宏观测量，我们还对grain-cu and ^<63,65> cu和 ^<27> a grain-allage nmr测量进行了NMR测量。从这些实验中，我们清楚地表明，cecual_3是一种抗铁磁体，NEEL温度为t_n = 2.5k，并且在每个Cu和al al位点提供的H_ <hf> k vs X绘图，1/T_1给出了F-Electron态的重要显微镜方面。 NMR测量还表明，Cecual_3在Banisn_3类型结构中结晶而不是BAAL_4型。我们还成功地将Cecuga_3的单晶具有与Cecual_3相同的晶体结构，并进行了上述测量。 We clarified that CeCuGa_3 is an antiferromagnet with T_N=4 K and the first energy splitting DELTA_1 in the crystal field splitting is several tens of degrees, It is much larger than 10K for CeCuAl_3.CeCuAl_3 lies in an interesting regime with competing T_K, RKKY exchange interaction T_<RKKY> and DELTA_1, each other.为了研究对这项竞争压力的影响，我们开发了高压NMR和磁化测量系统。高达15 kbar的压力中的NMR测量结果表明，Cecual_3的磁性特性受压力的强烈影响。随着压力的增加，T_K的值增加和T_N减少，抗铁路机构状态完全消失在10 kbar以上。 CECU_X（AL，GA）_ <4-X>系统的研究也在进行中。较少的

项目成果

H. Ido, T. Nishioka, M. Kontani: "Heavy fermion behavior in Th_2Zn_<17> type Ce_2Cu_xAl_<17-x> system" Czech. J. Phys.46・S4. 2071-2072 (1996)

H. Ido、T. Nishioka、M. Kontani：“Th_2Zn_<17> 型 Ce_2Cu_xAl_<17-x> 系统中的重费米子行为”，捷克 J. Phys.46・S4。

M.Kontani, N.Sugihara, K.Murase and N.Mori: "High pressure NMR of heavy fermion antiferromagnets CeAl_2 and CeCuAl_3" Czech.J.Phys.46 Suupl.2069-2070 (1996)

M.Kontani、N.Sugihara、K.Murase 和 N.Mori：“重费米子反铁磁体 CeAl_2 和 CeCuAl_3 的高压 NMR” Czech.J.Phys.46 Suupl.2069-2070 (1996)

H.Ido, T.Nishioka and M.Kontani: "Magnetic, transport and thermal properties of Ce_2Cu_xAl_<17-x>" Physica B. (in press). (1997)

H.Ido、T.Nishioka 和 M.Kontani：“Ce_2Cu_xAl_<17-x> 的磁性、输运和热性质”Physica B.（出版中）。

M. Kontani, T. Nishioka, H. Makino, K. Hayashi: "NMR and NQR studies on UCu_<4+x>Al_<8-x> (0≦x≦2) system" Physica B.(in press). (1997)

M. Kontani、T. Nishioka、H. Makino、K. Hayashi：“UCu_<4+x>Al_<8-x> (0≤x≤2) 体系的 NMR 和 NQR 研究” Physica B.（出版中） (1997)

S.Aoyama,H.Ido,T.Nishioka,M.Kontani: "NMR studies on heavy fermion CeCuAl_3 and CeCuGa_3" Czech.J.Phys.46・S4. 2069-2070 (1996)

S.Aoyama、H.Ido、T.Nishioka、M.Kontani：“重费米子 CeCuAl_3 和 CeCuGa_3 的 NMR 研究”Czech.J.Phys.46・S4（1996）。