Critical behaviour of gadolinium.
Date
1992
Authors
Bednarz, Grzegorz.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
A high-resolution, high-sensitivity, automated AC calorimeter capable of heat capacity measurements on very small samples (m $<$ 10 mg) with a temperature resolution of a few mK in the AC mode is described. This calorimeter also can be operated in the relaxation mode to provide absolute heat capacity values with precision and accuracy of around 2%. A microprocessor was employed to generate a stable oscillatory heating signal and to control the heater power, in order to improve the sensitivity of the measurement over other designs. A new very sensitive and miniature temperature probe (a film flake of a thermistor material), which increased measurement resolution and minimized the heat contribution of the addenda relative to other methods, was used.
This calorimeter was tested by measuring the heat capacity of gadolinium (Gd) over its ferromagnetic phase transition for several single crystals of Gd. The results agree well with the literature data giving, however, better resolution of the heat capacity in the critical region.
The critical behaviour of Gd was analyzed in terms of power laws with critical exponents and the logarithmic form expected for uniaxial dipolar systems. The results of the analysis are discussed and compared with other studies.
Thesis (Ph.D.)--Dalhousie University (Canada), 1992.
This calorimeter was tested by measuring the heat capacity of gadolinium (Gd) over its ferromagnetic phase transition for several single crystals of Gd. The results agree well with the literature data giving, however, better resolution of the heat capacity in the critical region.
The critical behaviour of Gd was analyzed in terms of power laws with critical exponents and the logarithmic form expected for uniaxial dipolar systems. The results of the analysis are discussed and compared with other studies.
Thesis (Ph.D.)--Dalhousie University (Canada), 1992.
Keywords
Chemistry, Inorganic., Engineering, Mechanical.