Experimental study of tricritical phenomena in the metamagnet ferrous chloride (FeCl₂)
Shang, Hen-Tai
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https://hdl.handle.net/2142/25533
Description
Title
Experimental study of tricritical phenomena in the metamagnet ferrous chloride (FeCl₂)
Author(s)
Shang, Hen-Tai
Issue Date
1980
Doctoral Committee Chair(s)
Salamon, Myron B.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
tricritical phenomena
metamagnet ferrous chloride
magneto-optical rotation
heat capacity
constant applied field
Language
en
Abstract
The magneto-optical rotation OF and heat capacity in constant applied field CHa have been simultaneously determined for the metamagnet
Ha FeC12, Since OF is proportional to magnetization we are able, for the
first time, to express both CHa and OF as functions of internal magnetic field along different isotherms. Following a detailed description of our experimental system, data are reported which were taken in the vicinity of the tricritical point at Tt=20.6K and in an applied field of Ha = 10.2kOe. Eight isotherms
t above the tricritical temperature T have been used to verify the
tricritical scaling hypothesis. A scaling function fur the magnetization is proposed, which is found to agree well with our experimental results. A scaling analysis of the heat capacity data is also shown to support the tricritical scaling hypothesis. Tricritical exponents extracted from this analysis are alpha t = 0.65± 0.05, theta = 2. and alpha = -0.35 ± 0.05.
For temperatures below T, light scattering and heat capacity CHa
have been simultaneously determined, both quantities are found to show discontineous changes at the mixed-phase boundaries. A theory which explains the step discontinuity in heat capacity CH 1s presented. The
a strong light scattering in the mixed-phase region has been used to determine the mixed-phase boundaries and result in the tricritical exponent 8u = 0.63 ± 0.05.
Tricritical exponents extracted from our data are found to be consistent with the scaling hypothesis and to satisfy the scaling laws, but to be in poor numerical agreement with mean-field predictions. We show that the agreement with theory can be improved by including logarithmic correction factors.
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