High-purity single-crystal growth and the research of heavy fermion superconductivity in Pr-based filled skutterudites

镨基填充方钴矿高纯单晶生长及重费米子超导研究

• 批准号: 15540347
• 负责人: SUGAWARA Hitoshi
• 金额: $ 2.37万
• 依托单位: The University of Tokushima (2004-2005)Tokyo Metropolitan University (2003)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540347/
• 关键词: filled skutterudite; highly correlated electron syste; heavy fermion superconductor; thermoelectric material; high-quality single crystal; electronic transport properties; magnetism; metal-insulator transition; ドハース・ファンアルフェン効果

We have prepared the high-quality single crystals of filled skutterudite RT_4X_<12> (R=rare earth, T=Fe,Ru,Os,X=P,As,Sb) and investigated the anomalous physical properties. Main results are summarized as below.1.Heavy fermion superconductivity of PrOs_4Sb_<12>2.Metal-insulator (M-I) transition of PrRu_4P_<12>3.Unusual heavy fermion state of SmOs_4Sb_<12>About PrOs_4Sb_<12>, we have measured the magnetoresistance for field along the three principal field directions and determined the magnetic field-temperature phases, from which we have confirmed the crystal electric field (CEF) ground state of Pr^3+ to be Γ_1 singlet. From inelastic neutron diffraction experiments, we have found the narrowing of the line widths of the magnetic excitations below the superconducting transition temperature, which is suggested the close connection between the superconductivity and the excitations. From the thermal conductivity measurements, we have found an anomalous feature of magnetic field dependence, f … More rom which we have proposed the multi band superconductivity of PrOs_4Sb_<12>.About PrRu_4P_<12>, to clarify the origin of M-I transition, we have measured the de Haas-van Alphen (dHvA) effect of the reference compound LaRu_4P_<12> and determined the Fermi surface (FS). We have found that the FS of LaRu_4P_<12> is basically the same with that of calculated FS of PrRu_4P_<12>, that is consistent with the localized nature of 4f electrons in PrRu_4P_<12>. Taking into account that LaRu_4P_<12> does not show the M-I transition, we have pointed out the essential role of correlation between the 4f- and conduction electrons cooperating with the FS nesting in driving the M-I transition of PrRu_4P_<12>. From inelastic neutron diffraction experiments, we have found that the 4f electron state far below the M-I transition temperature is described as well-defined CEF excitations, i.e., two different Pr-sites have different CEF each other, which explains the magnetic properties.About SmOs_4Sb_<12>, we have confirmed the bulk ferromagnetism below 3 K from NQR measurement, and found that this compounds is situated at the vicinity of ferromagnetic critical point in the pressure-temperature phase diagram from the resistivity measurements under pressure.For other filled skutterudites, such as SmRu_4P_<12> (M-I transition), CeOs_4Sb_<12> (Kondo semiconductor) etc., various experiments, such as electronic transport, dHvA effect, thermal and magnetic experiments, neutron diffraction, μSR,NMR. NQR, photoemission, optical conductivity, elastic, Mossbauer and Ramman scattering experiments are in progress to clarify the origin of the anomalous physical properties. Less

我们制备了高质量的填充方钴矿RT_4X_<12>（R=稀土，T=Fe,Ru,Os,X=P,As,Sb）单晶，并研究了其反常物理性质。 1.PrOs_4Sb_<12>的重费米子超导性2.金属-绝缘体(M-I)转变PrRu_4P_<12>3.SmOs_4Sb_<12>的异常重费米子态关于PrOs_4Sb_<12>，我们测量了沿三个主场方向的磁场磁阻，并确定了磁场-温度相位，由此我们确认了晶体根据非弹性中子衍射，Pr^3+ 的电场 (CEF) 基态为 Γ_1 单线态。实验中，我们发现在超导转变温度以下磁激励线宽变窄，这表明超导性与激励之间存在密切联系。从热导率测量中，我们发现了磁场依赖性的异常特征。 , f ... More ROM，我们提出了PrOs_4Sb_<12>的多能带超导性。关于PrRu_4P_<12>，澄清了由来M-I跃迁，我们测量了参考化合物LaRu_4P_<12>的德哈斯-范阿尔芬（dHvA）效应并确定了费米面（FS），我们发现LaRu_4P_<12>的FS与它基本相同。 PrRu_4P_<12> 的 FS，这与 PrRu_4P_<12> 中 4f 电子的局域性质一致。 LaRu_4P_<12>没有表现出M-I跃迁，我们通过非弹性中子衍射实验指出了4f-电子和传导电子之间的相关性与FS嵌套在驱动PrRu_4P_<12>的M-I跃迁中的重要作用。发现远低于 M-I 转变温度的 4f 电子态被描述为明确的 CEF 激发，即两个不同的Pr位点之间具有不同的CEF，这解释了其磁性。关于SmOs_4Sb_<12>，我们通过NQR测量证实了3 K以下的块体铁磁性，并发现该化合物位于铁磁临界点附近。压力下电阻率测量的压力-温度相图。对于其他填充方钴矿，例如 SmRu_4P_<12>（M-I 转变）， CeOs_4Sb_<12>（近藤半导体）等，电子输运、dHvA效应、热磁实验、中子衍射、μSR、NMR、光发射、光导、弹性、穆斯堡尔和拉曼散射实验等各种实验。澄清异常物理性质的起源的进展较少。

项目成果

T.Tayama et al.: "Magnetic Phase Diagram of the Heavy Fermion Superconductor PrOs_4Sb_<12>"Journal of Physical Society of Japan. Vol.72, No.6. 1516-1522 (2003)

T.Tayama等人：“重费米子超导体PrOs_4Sb_<12>的磁相图”日本物理学会杂志。

Magnetic Excitation in Heavy-Fermion Superconductor PrOs_4Sb_<12>

重费米子超导体 PrOs_4Sb_<12> 中的磁激发

• 发表时间: 2004
• 期刊: Journal of Physical Society of Japan Vol.73, No.6
• 作者: S.R.Saha et al.;K.Iwasa et al.;H.Sugawara et al.;H.Kotegawa et al.;K.Kuwahara et al.;G.Seyfarth et al.;S.R.Saha et al.;K.Iwasa et al.;H.Sugawara et al.;H.Kotegawa et al.;K.Kuwahara et al.;G.Seyfarth et al.;K.Kuwahara et al.;Y.Aoki et al.;S.Sanada et al.;H.Hidaka et al.;A.D.Huxley et al.;K.Kuwahara et al.
• 通讯作者: K.Kuwahara et al.

M.Kohgi et al.: "Evidence for Magnetic-field-induced Ordering in the Heavy Fermion Superconductor PrOs_4Sb_<12>"Journal of Physical Society of Japan. Vol.72, No.5. 1002-1005 (2003)

M.Kohgi 等人：“重费米子超导体 PrOs_4Sb_<12> 中磁场诱导有序化的证据”日本物理学会杂志。

Fermi Surface of LaRu_4P_<12> : A Clue to the Origin of the Metal-insulator Transition in PrRu_4P_<12>

LaRu_4P_<12> 的费米面：PrRu_4P_<12> 金属-绝缘体转变起源的线索

• 发表时间: 2005
• 期刊: Phys. Rev. B 71
• 作者: A.Yoshimi;H.Ueno et al.;H.Harima;S.Kimura;S.Kimura;H.Harima;S.R.Saha
• 通讯作者: S.R.Saha

Evolution of 4f electron states in the metal-insulater transition of PrRu_4P_12

PrRu_4P_12金属-绝缘体转变中4f电子态的演化

• 发表时间: 2005
• 期刊: Physical Review B Vol.72・No.2 (5pages)
• 作者: S.R.Saha et al.;K.Iwasa et al.
• 通讯作者: K.Iwasa et al.