Thermopower of spin glasses |
| |
Authors: | K H Fischer |
| |
Institution: | (1) Institut Laue-Langevin, 156X, F-38042 Grenoble, France |
| |
Abstract: | We calculate the thermopowerS
d(T) of spin glasses on the basis of thesd exchange model with additional interactions between the impurity spins by means of time dependent perturbation theory. Similarly to the Kondo effect, the observed giant thermopower can only be explained if one also takes into account the spin independent interactionV between the magnetic impurities and the conduction electrons. We obtain a Kondo termS
d
(1)
(T) (which reduces for vanishing spin interactions to the thermopower of Kondo systems) and in addition a resonance termS
d
(2)
(T) of opposite sign which vanishes for vanishing interactions. The superposition of both terms leads to an additional extremum of the total thermopower and to a change of sign at a temperatureT
0 which depends on the Kondo temperature and on the magnetic excitations of the spin glass and therewith on the freezing temperatureT
f. We obtain at low temperatures for oscillating and relaxing spin glass modesS
d
(1)
T2 andS
d
(2)
T. At high temperaturesS
d
(1)
(T) decreases as |lnT|–3 andS
d
(2)
asT
–1. A close relationship between the temperature dependent resistivity in Born approximation andS
d
(1)
(T) is pointed out.SFB 125 Aachen-Jülich-Köln |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|