Resistivity and specific heat measurements near phase transitions in metals
Simons, David Stuart
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https://hdl.handle.net/2142/29983
Description
Title
Resistivity and specific heat measurements near phase transitions in metals
Author(s)
Simons, David Stuart
Issue Date
1973
Doctoral Committee Chair(s)
Salamon, Myron B.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
resistivity
specific heat measurements
phase transition
Language
en
Abstract
The ac calorimetry technique for measuring the specific heat has been
modified to include a simultaneous measurement of the temperature derivative
of the electrical resistivity on the same sample. Measurements are reported
on f3-brass and gadolinium.
The resistivity derivative of f3~brass is found to be proportional to
the specific heat through its order-disorder transition temperature of
466°C. This is in agreement with an extension of the theoretical prediction
that the quantities should be proportional in a magnetic system.
Measurements of the specific heat and resistivity derivative on the
rare earth ferromagnet gadolinium have revealed a previously undetected
anomaly in the specific heat along with a peak in the a-axis resistivity
derivative at 226°K, where the magnetization vector tilts from the c-axis.
The anomalies are suppressed in applied magnetic fields. A model for the
temperature dependence of the anisotropy energy is used to describe this
tilting transition.
Near the Curie temperature of 29l °K, measurements of the specific
heat and a-axis resistivity derivative of gadolinium are made in several
applied magnetic fields in order to cancel background effects and establish
the predicted proportionality. Kinks in the specific heat in small
applied fields are explained by demagnetizing effects. At higher fields,
the specific heat is compared with the prediction of the linearized
parametric equation of state, with inconclusive results.
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