Acta Geodaetica, Geophysica et Montanistica 12. (1977)

1–3. szám - VIII. Laboratory studies of the temperature dependence of the conductivity of rocks - Laštovičková, M.: The temperature dependence of the electrical conductivity of basaltic rocks from Bohemian Massif

Acta GeodaetGeophys. et Montanist. Acad. Sei. Hung. Tomus 12 (1 — 3), pp. 417—422 (1977) VIII. Laboratory studies of the tempera ture dependence of the conductivity of rocks THE TEMPERATURE DEPENDENCE OF THE ELECTRICAL CONDUCTIVITY OF BASALTIC ROCKS FROM BOHEMIAN MASSIF M. laStoviCková G EOPHYSICAL INSTITUTE, CZECHOSL, ACAD. SCI. PRAHA, CZECHOSLOVAKIA The paper discusses the electrical conductivity of basalts, hematites and magnetites in the vicinity of the Curie temperature. The decrease of the conductivity increase vs. temperature, or even its local decrease enables to determine the Curie temperature from the temperature dependence of the conductivity. The changes of the electrical conductivity in the vicinity of the Curie temperature can be qualitatively explained by the quantummechanical ferrimag­­netic model. The temperature dependence of the electrical conductivity of some rocks displays deviations from linearity in the temperature interval of 250—700 °C. Some authors [1, 2] have pointed out that these deviations may be associated with the changes of the electrical conductivity of the ferromagnetic minerals contained in the rocks, in the vicinity of their Curie temperature. In order to explain these possible associations Turov’s [3] model was employed to elaborate a quantum theory of changes of the electrical con­ductivity in the vicinity of Curie temperature. Using the second quantization it was determined that in the interval of temperatures below Curie tempera­ture of ferromagnetic minerals the expression for the conductivity would read: ln., = b2*,-4±*£j T <& 2kT and for temperatures higher than Curie temperature, T 0, where fi = 0: In o’,- = In 2a'0 — (a®/2kT) n‘ [I being the magnetization, at the conductivity of the i-th type of carrier, n‘ number of carriers of the i-th type, an and a'0 material parameters, a® and a(­­the appropriate activation energies. From this follows the decrease of the activation energy in the interval above Curie temperature which is charac­terized by the term: (a>/2kT) n‘ the product a '(fin1 representing the overall change of the activation energy. This theory will be published elsewhere. 27 Acta Geodaetica, Geophysica et Montanistica Acad. Sei. Hung. 12, 1977

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