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Unique Behavior of Seebeck Coefficient in N‐Type CdCr2Se4

 

作者: A. Amith,   G. L. Gunsalus,  

 

期刊: Journal of Applied Physics  (AIP Available online 1969)
卷期: Volume 40, issue 3  

页码: 1020-1022

 

ISSN:0021-8979

 

年代: 1969

 

DOI:10.1063/1.1657511

 

出版商: AIP

 

数据来源: AIP

 

摘要:

Electrical resistivities &rgr;, normal Hall coefficientsR0, and Seebeck coefficientsQ, are reported for a series of samples of the semiconducting ferromagnetic compound CdCr2Se4, doped with varying amounts of indium. The behavior of &rgr; and ofR0indicates that from room temperature down to 150°K the electrons deionize onto the donor centers. From 150°K down to about 55°K, the carrier concentration increases by approximately four orders of magnitude, accompanied by a proportional drop in &rgr;; this can be attributed to the known decrease in bandgap with lowering ofT, if the donor level is assumed to remain constant with reference to the valence‐band edge. The rise of &rgr; below 55°K is ascribed to impurity conduction. The mobilities reach a maximum nearTc, and fall off on both sides. Strong dependence ofR0on the magnetic fieldHis found above 110°K. The magnetoresistance is negative, and peaks sharply at 130°K; it obeys different power laws on the two sides of its peak. The Seebeck coefficientQshows unique dependence onT, Hand on In content: it displays local extrema at 150°K and at 125°K. Between these two temperatures,Hhas a strong effect onQ, depending on the In concentration. No simple relation between the behavior ofQon the one hand, and of &rgr; andR0on the other, has been deduced. The model suggested by the data requires two bands, with charge carriers whose concentrations and mobilities are very different and have strong dependencies onT.

 

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