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Measurement for Transport and Thermal Properties of Materials with anomalous thermoelectric behaviors at Low Temperatures below 1K

1K以下低温下异常热电行为材料的输运和热性能测量

基本信息

批准号：
15540335
负责人：
KUWAI Tomohiko
金额：
$ 2.05万
依托单位：
Toyama University
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 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540335/
关键词：
high resolution specific heat measurement Non-Fermi liquid low-temperature thermoelectric power strongly correlated electron systems single crystal growth Thermal conductivity low-temperature specific heat under high pressure material resear

项目摘要

Aim for our research is as follows :1.Construction of the measurement systems for thermoelectric power S, thermal conductivity κ and the other physical quantities characterizing properties of solid from the room temperature down to 0.1K.2.Identification of materials with anomalous thermoelectric properties at low temperatures, and research for their nature via transport and thermal quantities such as electrical resistivity p and specific heat C.In the research term, we finished constructing the several systems including S and κ on a ^3He-^4He dilution frigerator, C under pressure using a ^3He-cryostat, and investigated the magnetic properties of several 4f-electron compounds from experimental results obtained using these systems. The main research results are as follows :1.We measured S and C of Ce(Ni,Pd)_2Ge_2 well below 1 K, and detected a quantitative close relation in between the Sommerfeld coefficient γ and the S/T reflecting a non-Fermi liquid nature in the lowest temperature range.2.Mitsuda et al. reported the pressure-induced ferromagnetic transition at 2 K with small magnetic moment in a valence transition compound (Yb_<0.8>Y_<0.2>)InCu_4 by magnetization measurement. We detected a sharp peak at 2 K in C under 1.2 GPa, and obtained about 20 % of the full moment of Yb^<3+> ion is frozen with this phase transition from the entropy consideration, concluding this transition is from a bulk property and intrinsic in this compound.3.We measured p and C of a valence fluctuator EuPd_2Si_2 and its 'isovolume' diluted alloys (Eu(La_<0.67>Y_<0.33>)Pd_2Si_2 between 2 and 300 K. We found both the resistance minimum at 20 K and the C/T upturn reaching large amount at low temperatures below 30 K for the alloys beyond 25 % of substitution of Eu by (La_<0.67>Y_<0.33>). We consider they may originate from the Kondo effect, and the measurements of S for these alloys are in progress.

我们的研究目的如下：1.建立了从室温到0.1K的热电功率S、热导率κ等表征固体性质的物理量的测量系统。2.鉴定了低温下具有异常热电性质的材料，并通过输运和热学量如电阻率p和比热C研究了它们的性质。并从使用这些系统获得的实验结果研究了几种4f-电子化合物的磁性。主要研究结果如下：1.Ce（Ni，Pd）_2Ge_2的S和C在低于1 K的温度下测量，发现索末菲系数γ与S/T之间存在定量的密切关系，反映了在最低温度范围内的非费米液体性质<0.8><0.2>。在1.2GPa下，我们在2K处检测到了C的一个尖峰，从熵的角度考虑，Yb^<3+>离子的全磁矩约有20%被冻结在这一相变中，从而得出这一相变是由该化合物的体性质和本征性质引起的结论。3.我们在2 - 300 K之间测量了价态涨落体EuPd_2Si_2及其“等体积”稀释合金（Eu（La_<0.67>Y_<0.33>）Pd_2Si_2）的p和C。发现当（La_ Y_）取代Eu超过25%时，合金的电阻在20 K时达到最小值，而C/T在低于30 K的低温下有较大幅度的上升<0.67><0.33>。我们认为它们可能起源于近藤效应，并且这些合金的S的测量正在进行中。