Ultrasonic Study of rattling in clathrate compounds

笼形化合物中嘎嘎声的超声研究

• 批准号: 17540318
• 负责人: NEMOTO Yuichi
• 金额: $ 2.18万
• 依托单位: Niigata 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-17540318/
• 关键词: Strongly Correlated Electron Systems; Ultrasound; Rattling; Quadrupole; Clathrate Compounds; Superconductivity; Low-Temperature Experiment; Solid State Physics; 磁性; 低温; スクッテルダイト; 低温物性

1)We previously observed ultrasonic disperSi_6n due to rattling in heavy-fermion superconductor PrOs_4Sb_<12>. Furthermore, elastic softening proportional to the 1/T was found below 4 K down to T_c=1.85 K, which is attributed to off-center tunneling of Pr ion in a cage. These results support that the strong correlation between rattling/tunneling and heavy-fermion and it's superconductivity in PrOs_4Sb_<12>.2)We have made ultrasonic experiments of the Ru substitutional Pr(Os_<1-x>RuX)_4Sb_<12>. As a result, ultrasonic disperSi_6n becomes weak with more substitution of Ru concentration and completely disappears in BCS superconductor PrRu_4Sb_<12>. We proposed that the coupling between the off-center tunneling and conduction electrons will cause the heavy-fermion state and superconductivity in PrOs_4Sb_<12>.3)We have examined LaOs_4Sb_<12> without 4f-electron in order to investigate the correlation between rattling and 4f electrons. Ultrasonic disperSi_6n in C_<11> was clearly observed, t … More hat means rattling appears without 4f-electron. We conclude that the coupling between off-center mode and surrounding conduction electrons is crucial for the rattling and tunneling.4)We have measured elastic constants of NdOs_4Sb_<12> with three 4f electrons. Two distinct ultrasonic disperSi_6ns around 40 K and 15 K were observed in C_<11>. This result indicates that multiple structure of anharmonic potential is formed in a cage as it were, illustrated by two deferent activation energy E and characteristic time τ_0 of the rattling in NdOs_4Sb_<12>.5)We have observed elastic softening of C_<11> and C_<44> proportional to the 1/T at low temperatures in NdOs_4Sb_<12>. According to the analysis using quadrupolar susceptibility, we confirmed that the ground state of the crystal field levels of 4f^3 electronic state is Γ_<67> quartet in NdOs_4Sb_<12>.6)We have performed ultrasonic measurements of isomorphic compound La_3Pd_<20>Si_6 and Ce_3Pd_<20>Si_6 to study rattling and tunneling. As a result, no ultrasonic dispersions were found in La_3Pd_<20>Si_6 and Ce_3Pd_<20>Si_6 contrary to our previous results of R_3Pd_<20>_Ge6. Here we report that the importance of the conduction bands as well as clathrate structure for the occurrence of rattling and tunneling.7)We have observed elastic softening of (C_<11>-C_<12>)/2 and C_<44> proportional to the 1/T at low temperatures in Ce_3Pd_<20>Si_6. We obtained crystal field levels by use of quadrupolar susceptibility to be a Γ_8 quarter ground at 8c site and a Γ_7 doublet ground at 4a site, respectively. Furthermore, we revealed that the presence of antiferro-quadrupolar ordering phase in magnetic fields. Less

1）我们以前在重费米子超导体PrOs_4Sb_中观察到了由于振动引起的Si_6n的超声色散<12>。此外，在低于4K至Tc = 1.85K的温度范围内，Pr离子的弹性软化与1/T成正比，这是由于Pr离子在笼中的偏心隧穿引起的。这些结果支持了PrOs_4Sb_中重费米子和重费米子之间的强相关性及其超导电性<12>。2）对Ru取代的Pr（Os_ RuX）_4Sb_进行了超声实验<1-x><12>。结果表明，在BCS超导体PrRu_4Sb_2中，随着Ru浓度的增加，Si_6n的超声弥散逐渐减弱，并完全消失<12>。我们提出了在PrOs_4Sb_中，偏离中心的隧穿电子和传导电子之间的耦合是导致重费米子态和超导电性的原因<12>。3）我们研究了<12>没有4f电子的LaOs_4Sb_，研究了4f电子与晶格振动之间的关系。超声分散Si_6n在C_2中的<11>分布清晰可见， ...更多信息 这意味着在没有4f电子的情况下出现了晶格振动，我们认为偏离中心模与周围导电电子之间的耦合是晶格振动和隧穿的关键<12>。在40 K和15 K附近观察到两种明显的超声分散<11>。结果表明，NdOs_4Sb_3中的非简谐势在笼中形成了多重结构，表现为两个不同的振动激活能E和特征时间τ_0<12>。5）观察到NdOs_4Sb_3中<11>C_3和C_4<44>在低温下的弹性软化与1/T成正比<12>。根据四极极化率的分析，我们确定了NdOs_4Sb_中4f^3电子态的晶体场能级的基态为Γ_<67>四重<12>态。6）我们对<20>La_3Pd_Si_6和Ce_3Pd_Si_6<20>的晶格振动和隧穿进行了超声测量。结果表明，在La_3Pd_Si_6和Ce_3Pd_Si_6中没有发现超声分散现象<20><20>，这与我们以前对R_3Pd_Ge_6的研究结果相反<20>。7）在Ce_3Pd_Si_6中观察到低温下（C_<11>-C_<12>）/2和C_<44>（1/T<20>）的弹性软化。我们利用四极极化率得到了晶体场能级，在8 c位为四分之一基态，在4a位为四分之一基态。此外，我们揭示了磁场中反铁四极有序相的存在。少

项目成果

Magnetic anisotropy of antiferro-quadrupole ordering in tetragonal HoB_2C_2

四方HoB_2C_2中反铁四极有序的磁各向异性

• 发表时间: 2005
• 期刊: Physica B 359-361
• 作者: T.Yanagisawa;T.Goto;Y.Nemoto;R.Watanuki;K.Suzuki;O.Suzuki;G.Kido
• 通讯作者: G.Kido

Magnetic phase diagram of Ce_xLa_<1-x>B_6 in high magnetic fields

Ce_xLa_<1-x>B_6在强磁场中的磁相图

• 发表时间: 2007
• 期刊: J. Magn. Magn. Mater. 310
• 作者: Mitsuhiro Akatsu;Nanako Kazama;Terutaka Goto;Yuichi Nemoto;Osamu Suzuki;Giyuu Kido;Satoru Kunii
• 通讯作者: Satoru Kunii

Riseborough, Observation of two spin gap energies in the filled skutterudite compound CeOs_4Sb_<12>

Riseborough，填充方钴矿化合物 CeOs_4Sb_<12> 中两种自旋间隙能量的观察

• 发表时间: 2007
• 期刊: Phys.Rev.B 75
• 作者: D.A.Adroja;J.-G.Park;E.A.Goremychkin;K.A.McEwn;N.Takeda;B.D.Rainford;K.S.Knight;J.W.Taylor;Jeongmi Park;H.C.Walker;R.Osborn;Peter S.
• 通讯作者: Peter S.

Observation of Low-Temperature Elastic Softening due to Vacancy in Crystalline Silicon

晶体硅中空位引起的低温弹性软化的观察

• 发表时间: 2006
• 期刊: J. Phys. Soc. Jpn. 75
• 作者: T.Goto;H.Y.Kaneta;Y.Saito;Y.Nemoto;K.Sato;K.Kakimoto;S.Nakamura
• 通讯作者: S.Nakamura

Direct observation of vacancy in silicon using sub-Kelvin ultrasonic measurements

使用亚开尔文超声波测量直接观察硅中的空位

• 发表时间: 2006
• 期刊: Materials Science and Engineering B 134
• 作者: Terutaka Goto;Hiroshi Yamada-Kaneta;Yasuhiro Saito;Yuichi Nemoto;Koji Sato;Koichi Kakimoto;Shintaro Nakamura
• 通讯作者: Shintaro Nakamura