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Pressure-Induced Magnetic Phase of 4f Hole Systems with a Geometrical Frustration

具有几何挫败的 4f 孔系统的压力感应磁相

基本信息

批准号：
17540330
负责人：
UMEO Kazunori
金额：
$ 2.18万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17540330/
关键词：
Frustration Pressure Specific heat Electrical resistivity Magnetization Heavy-Fermion system Kondo effect 磁場 YbRhSb YbAgGe メタ磁性

项目摘要

The purpose of this study is to investigate the origin of a pressure -induced magnetic phase of heavy-fermion compounds, YbAgGe and YbRhSb, which can not be understood by a competition between Kondo effect and RKKY interaction.1. In the case of YbAgGe, the Yb ions form a quasikagome lattice in the hexagonal c plane of the ZrNiAl-type structure. This compound undergoes two magnetic phase transitions at T_<M1> = 0.8 K (second order) and T_<M2> = 0.65 K (first order). For P > 1.6 GPa, the T_M increases abruptly. In order to examine the origin of the pressure-induced phase transition of YbAgGe, specific heat measurements have been performed up to 3 GPa by an ac calorimeter which we have developed using a Bridgman anvil cell. A cusp of C(T) at T_<M2> = 0.75 K for P = 0.29 GPa changes to the large and sharp peak of C at T_<M2> for P = 1.15 GPa. For P > 2 GPa, a distinct jump of C(T) at T_<M3> is a characteristic behavior for a second-order magnetic transition observed in compounds without ge … More ometrical frustration. The magnetic entropy at T_m, S_m(T_m), estimated by the specific heat data increases above 1.6 GPa. The pressure-independence of S_m, for T > T_m, suggests that the increase of S_m(T_m) and Tm with pressure for P > 1.6 GPa is attributed to a partial release of the magnetic frustration, not decrease of the Kondo temperature with pressure.2. YbRhSb with an orthorhombic ω-TiNiSi type structure undergoes at ambient pressure a transition into an unusual magnetic state at T_M = 2.7 K, which is associated with very small spontaneous moment of 3 x 10^<-3> μ_B/Yb. The resistivity measurement under pressure revealed that T_M(P) has a pronounced minimum of 1.8 K at P_c = 1.6 GPa.^<5)> In order to investigate the pressure induced transition of the ground state above 1.6 GPa, ac magnetic susceptibility and DC magnetization and specific heat measurements have been carried out up to 3GPa. With increasing pressure, the value of M increases, and the metamagnetic like anomaly observed at B_M = 3.2 T for P = 0 becomes clearer and shifts to low fields. The extrapolation of B_M(P) goes to B_M = 0 at about 2 GPa. Above 2 GPa, the antiferromagnetic phase with metamagnetic behavior changes to a ferromagnetic phase. Less

本研究的目的是研究重费米子化合物YbAgGe和YbRhSb的压力诱导磁相的起源，这是不能通过近藤效应和RKKY相互作用之间的竞争来理解的。1．在YbAgGe的情况下，Yb离子在ZrNiAl型结构的六方c面中形成准卡戈格晶格。该化合物在 T_<M1> = 0.8 K（二阶）和 T_<M2> = 0.65 K（一阶）处经历两次磁相变。当 P > 1.6 GPa 时，T_M 突然增加。为了检查 YbAgGe 压力诱导相变的起源，我们使用布里奇曼砧室开发的交流热量计进行了高达 3 GPa 的比热测量。 P = 0.29 GPa 时，T_<M2> = 0.75 K 处的 C(T) 尖点变为 P = 1.15 GPa 时 T_<M2> 处 C 的大且尖锐的峰值。对于 P > 2 GPa，T_<M3> 处 C(T) 的明显跳跃是在没有几何挫败的化合物中观察到的二阶磁转变的特征行为。由比热数据估计的 T_m 处的磁熵 S_m(T_m) 增加到 1.6 GPa 以上。当T > T_m 时，S_m 与压力无关，表明当P > 1.6 GPa 时，S_m(T_m) 和Tm 随着压力的增加归因于磁挫败的部分释放，而不是近藤温度随压力的降低。2．具有正交ω-TiNiSi型结构的YbRhSb在环境压力下在T_M = 2.7 K时转变为异常磁态，这与3 x 10^<-3> μ_B/Yb的非常小的自发矩相关。压力下的电阻率测量表明，在 P_c = 1.6 GPa 时，T_M(P) 的最小值为 1.8 K。^<5)> 为了研究 1.6 GPa 以上压力引起的基态转变，我们进行了高达 3 GPa 的交流磁化率、直流磁化强度和比热测量。随着压力的增加，M值增加，P = 0时B_M = 3.2 T处观察到的类变磁异常变得更加清晰，并转向低场。 B_M(P) 的外推法在大约 2 GPa 时达到 B_M = 0。高于 2 GPa，具有变磁行为的反铁磁相转变为铁磁相。较少的

项目成果

期刊论文数量（18）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Specific-Heat Measurement above 3 GPa using a Bridgman Anvil Cell

使用布里奇曼砧池进行高于 3 GPa 的比热测量

DOI：
发表时间：
2007
期刊：
Journal of the Physical Society of Japan (印刷中)
影响因子：
0
作者：
Keisuke;Mitsumoto;H.Kubo
通讯作者：
H.Kubo

Anisotropic 4f-spin dynamics across the B-T phase diagram of Ce7Ni3

Ce7Ni3 B-T 相图上的各向异性 4f 自旋动力学

DOI：
发表时间：
2006
期刊：
J. Phys. : Cond. Matter 18
影响因子：
0
作者：
A.Schenck
通讯作者：
A.Schenck

Pressure- and field-induced magnetic instabilities in a heavy-fermion antiferromagnet Ce_7Ni_3

重费米子反铁磁体 Ce_7Ni_3 中压力和场引起的磁不稳定性

DOI：
发表时间：
2005
期刊：
Journal of Alloys and Compounds (印刷中)
影响因子：
0
作者：
K.Umeo et al.;K.Umeo et al.
通讯作者：
K.Umeo et al.

Pressure-and Field-Induced Non-Fermi-Liquid Behaviors in a Heavy-Fermion Antiferromagnet Ce7Ni3

重费米子反铁磁体 Ce7Ni3 中压力和场诱导的非费米液体行为

DOI：
发表时间：
2007
期刊：
Journal of Low Temperature Physics 174
影响因子：
0
作者：
K.Sugiyama;H.Nakashima;D.Aoki;S.Ikeda;Y.Haga;E.Yamamoto;A.Nakamura;Y.Homma;Y.Shiokawa;K.Kindo;M.Hagiwara;Y.Onuki;K.Umeo;杉山清寛;H.Kubo;Winfried Koller;K.Umeo
通讯作者：
K.Umeo

Double phase transition in the heavy-fermion system Ce_4Ni_3Pb_4

重费米子体系Ce_4Ni_3Pb_4中的双相变