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thermopower and its magnetic field effect on Ce and Sm compounds having a resistivity behavior of divergent type

热电势及其磁场对具有发散型电阻率行为的 Ce 和 Sm 化合物的影响

基本信息

批准号：
03640316
负责人：
SAKURAI Junji
金额：
$ 1.15万
依托单位：
Toyama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

The Kondo compounds of cerium and samarium show very often the typical increase of resisitivity due to Kondo scattering at low temperatures. Some show a decrease of resistivity due to the onset of coherence of Kondo scattering or a heavy electron state, and some show a sudden and rapid decrease due to the onset of magnetic order at lower temperature. In addition, a sharp critical type resistivity peak is observed in some cases, at the onset of magnetic order. Moreover, some comounds like CeNiSn show a resistivity increase of a semiconductor type due to a gap formation of an origin of Kondo scattering. Thus, the resistivity behavior of Kondo compounds are of various types.However, the resistivity measurements alone can not tell the origin of its anomalies because of too much complications of similar effects. Our aim of present study is to systematically measure the thermopower in addition to the resistivity and to have an unified picture of the phenomena of Kondo compounds.In this study, we have prepared a large number of new Ce compounds having a chemical formula CeTX (T=Ni, Pd or Pt, X=Sn, In or Ge) and measured their resistivity and thermopower. The results are full of variety showing characteristic and different nature of Kondo effect of each compound. We found a close relation of an initial slope of thermopower and the electronic specific heat at low temperature. We found some of typical types of thermopower behavior of Kondo compounds at the ferromagnetic Curie temperature or at the antiferromagnetic Neel temperature. However, as for Sm compounds, those we have studied mostly did not show Kondo effects. Further study must be carried out for Sm compounds.

铈和钐的近藤化合物在低温下经常表现出由于近藤散射而导致的典型的电阻率增加。有些由于近藤散射相干性的开始或重电子态的开始而表现出电阻率的下降，有些由于较低温度下磁序的开始而表现出突然而迅速的下降。此外，在某些情况下，在磁序开始时观察到一个尖锐的临界型电阻率峰值。此外，一些化合物如CeNiSn显示出半导体类型的电阻率增加，这是由于近藤散射的起源形成的间隙。因此，近藤化合物的电阻率行为是多种类型的。然而，由于相似效应的复杂性，单靠电阻率测量并不能说明其异常的来源。我们本研究的目的是系统地测量除电阻率外的热功率，并对近藤化合物的现象有一个统一的认识。在本研究中，我们制备了大量化学式为CeTX （T=Ni， Pd或Pt， X=Sn， In或Ge）的新型Ce化合物，并测量了它们的电阻率和热功率。结果显示出各种化合物近藤效应的特点和不同性质。我们发现热功率的初始斜率与低温下的电子比热有密切的关系。我们发现了近藤化合物在铁磁居里温度或反铁磁尼尔温度下的一些典型热能行为。而对于Sm化合物，我们所研究的大都没有近藤效应。需要对Sm化合物进行进一步的研究。