Low-Temperature Thermomagnetic Effects in Graphite

1972 ◽  
Vol 50 (20) ◽  
pp. 2444-2450 ◽  
Author(s):  
J. P. Jay-Gerin
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Thermoelectric Power ◽  
Satisfactory Agreement ◽  
Quantum Mechanical ◽  
Phonon Drag ◽  
Phonon Coupling

The low-temperature thermoelectric power (TEP) and the Nernst–Ettingshausen (NE) coefficient of graphite due to phonon drag are studied in the presence of a magnetic field H directed along the c axis and small enough for the quantum-mechanical character of the motion of the carriers to be negligible. Expressions for the TEP and the NE coefficient are obtained on the basis of the theory of Jay-Gerin and Maynard, in which the phonon-drag TEP of graphite in the absence of a magnetic field is linked with the Kohn screening anomaly. The results suggest a method by which information might be obtained about the strength of the electron– and hole–phonon coupling directly from experiment. A satisfactory agreement is found with the measurements of Takezawa, Tsuzuku, Ono, and Hishiyama and of Tamarin, Shalyt, and Volga.

THE THERMOELECTRIC POWER OF ANNEALED AND COLD-WORKED SILVER AND GOLD AT LOW TEMPERATURES

1960 ◽  
Vol 38 (8) ◽  
pp. 1048-1058 ◽  
Author(s):  
W. B. Pearson
Keyword(s):  
Low Temperature ◽  
Thermoelectric Power ◽  
Low Temperatures ◽  
Phonon Drag ◽  
Scattering Mechanisms ◽  
Cold Worked

Most of the low-temperature thermoelectric behavior of annealed and cold-worked silver and gold samples can be accounted for satisfactorily by using Kohler's equation, S = ΣWiSi/ΣWi, to calculate as a function of temperature the diffusion thermoelectricity under the influence of various competing scattering mechanisms in the metals, and by taking account of the phonon-drag contribution to the thermoelectricity. New data are presented and interpreted.

Magnon drag and the low temperature thermopower of GeMnTe

1978 ◽  
Vol 56 (5) ◽  
pp. 497-500
Author(s):  
A. Cafaro ◽  
F. T. Hedgcock ◽  
W. B. Muir
Keyword(s):  
Low Temperature ◽  
Experimental Evidence ◽  
Thermoelectric Power ◽  
Low Temperatures ◽  
Impurity Scattering ◽  
Experimental Results ◽  
Phonon Drag ◽  
Degenerate Semiconductors ◽  
Upper Limit

The thermoelectric power of pure GeTe and GeMnTe containing 1 and 5at.% Mn has been measured between 25 and 2.5 K. The manganese doped Ge–Te alloys ferromagnetically order at low temperatures and theoretical estimates of the magnon drag contribution to the thermopower in these degenerate semiconductors is 60 μV/K. When appropriate allowance is made for the effects of impurity scattering on the phonon drag thermopower there appears to be no experimental evidence for a magnon drag contribution to the thermopower of this magnitude. An upper limit for the magnon drag contribution to the thermopower estimated from the experimental results for these materials is 0.5 μV/K.

Magnetic Field Dependence of the Thermoelectric Power of Iron

1972 ◽  
Vol 50 (22) ◽  
pp. 2836-2839 ◽  
Author(s):  
F. J. Blatt
Keyword(s):  
Magnetic Field ◽  
Thermoelectric Power ◽  
Magnetic Field Dependence ◽  
Cold Work ◽  
Transverse Magnetic ◽  
Band Model ◽  
Spin Orbit Coupling ◽  
Phonon Drag ◽  
Domain Alignment ◽  
Two Band Model

The thermoelectric power of iron exhibits a broad maximum of about 17 µV/K near 200 K. The relatively high temperature of this maxim and its dependence on alloying and cold work argue against phonon drag as the mechanism responsible for this peak. Recently, MacInnes and Schröder proposed that this peak derives from anisotropic (scew) scattering due to spin–orbit coupling, which may be simulated by a large effective transverse magnetic field. Their calculations, which reproduce experimental observations quite well, are based on an expression derived by Sondheimer that is valid for an ideal two-band model. According to this model and the suggestion of MacInnes and Schröder, the thermoèlectric power of iron should be strongly influenced by domain alignment. Measurements of the dependence of the thermoelectric power of iron in transverse and longitudinal magnetic fields reported here yield results contrary to the predictions of that model.

LOW-TEMPERATURE THERMOELECTRIC POWER OF HEAVILY DOPED n-TYPE GERMANIUM

1965 ◽  
Vol 43 (11) ◽  
pp. 2008-2020 ◽  
Author(s):  
F. T. Hedgcock ◽  
D. P. Mathur
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Thermoelectric Power ◽  
Temperature Region ◽  
Magnetic Scattering ◽  
Zero Magnetic Field ◽  
Large Temperature ◽  
Susceptibility Data ◽  
Antiferromagnetic Ordering ◽  
Heavily Doped

A large, temperature-dependent component in the low-temperature thermoelectric power of heavily doped n-type germanium has been observed in the temperature region of liquid helium. All of the samples (6.8–62 × 1017 per cm3) exhibit a negative magnetoresistance in the low-temperature region which saturates at reasonably low magnetic-field values. On the basis of an assumed magnetic scattering, the magnetoresistance and magnetic susceptibility data have been analyzed in order to estimate the magnitude and concentration of the localized magnetic moment of the spin-scattering center, and also to estimate the exchange integral giving rise to the coupling between the mobile carriers and the localized impurity electrons. The resistivity behavior, in both a finite and zero magnetic field, appears to be best described by assuming an antiferromagnetic transition in the region of the thermoelectric anomaly. Attempts are made to interpret the observed temperature dependence of the thermopower. However, as yet, there is no quantitative theory to predict the thermoelectric behavior of a degenerate semiconductor in the presence of antiferromagnetic ordering.

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