Document Type

Dissertation

Date of Award

1974

Keywords

Ferromagnetism, Magnetoresistance, Paramagnetism, Curie temperature

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Tsu-ming Wu

Second Advisor

Newton I. Greenberg

Third Advisor

Robert L. Pompi

Series

Science and Mathematics

Abstract

We have investigated the resistivity anomalies of ferromagnetic metals at the Curie point using the itinerant model. The nature of these resistivity anomalies is related to phase transitions of second kind. Current theory describing these anomalies is based on the localized model of the magnetic electrons in ferromagnetic metals. There is an ansatz in solid state physics that if the magneto-resistance can be explained by the realistic itinerant model, the localized model should give the same result.

In this work, we use the itinerant model to treat the spin correlation function. Using the second quantization techniques of field theory, the correlation function is found. Thence, the scattering cross section is obtained. Based on transport theory, the relaxation time and the resistivity are calculated for both the paramagnetic and the ferromagnetic regions. The temperature derivatives of the resistivity are then derived for temperatures approaching the Curie temperature from both below and above. Our results are exactly the same as obtained by the localized model, namely, positive infinite for T approaching Tc from below and negative infinite for T approaching Tc from above. Therefore, our itinerant model calculation confirms the above ansatz.

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