2026-09-24T14:12:43Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/82862022-01-13T07:54:41Zcom_1721.1_7582com_1721.1_7581col_1721.1_131022
Robert J. Birgeneau.
Christianson, Rebecca J. (Rebecca Jean), 1973-
Massachusetts Institute of Technology. Dept. of Physics.
Massachusetts Institute of Technology. Department of Physics
2005-08-23T18:53:47Z
2005-08-23T18:53:47Z
2001
2001
http://hdl.handle.net/1721.1/8286
50420210
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2001.
In title on t.p., double-underscored "x" appears as subscript.
Includes bibliographical references (p. 111-115).
This thesis presents results of two scattering studies of low dimensional magnetic materials. The first is a neutron scattering study of Rb2MnF4, a nearly ideal two-dimensional square lattice Heisenberg antiferromagnet with S = 5/2. When this material is placed in a magnetic field on an extrapolation of the spin-flop phase boundary into the paramagnetic phase, Heisenberg critical behavior can be accessed to a much longer correlation length than had previously been achieved for a high-spin system. Comparison of our results with current theories indicate that the probed temperature region lies in a crossover region from classical to renormalized classical behavior. In addition, we show measurements of both the quasielastic and magnon dynamic behavior. The second part of this thesis presents extensive synchrotron x-ray scattering measurements of the high-field incommensurate phase in doped CuGeO3. Random-field behavior, including Lorentzian-squared lineshapes, the changing of a first order transition to second-order, and critical destruction of long-range order is observed in this continuous order parameter system.
by Rebecca J. Christianson.
Ph.D.
115 p.
7400394 bytes
7400155 bytes
application/pdf
application/pdf
eng
Massachusetts Institute of Technology
M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.
http://dspace.mit.edu/handle/1721.1/7582
Physics.
X-ray and neutron scattering studies of the Rb₂MnF₄ and Cu₁âõxMgx̳GeO₃ in an external magnetic field
Thesis
application/pdf
false
Publication
unknown
unknown
<Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="953fed81-4315-4bcc-a0d1-141637a408ab">
<Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type>
<Language>eng</Language>
<Title>X-ray and neutron scattering studies of the Rb₂MnF₄ and Cu₁â‚‹õxMgx̳GeO₃ in an external magnetic field</Title>
<PublishedIn>
<Publication>
</Publication>
</PublishedIn>
<PublicationDate>2001</PublicationDate>
<Authors>
<Author>
<DisplayName>Christianson, Rebecca J. (Rebecca Jean), 1973-</DisplayName>
<Affiliation>
<OrgUnit>
</OrgUnit>
</Affiliation>
</Author>
</Authors>
<Editors>
</Editors>
<Publishers>
<Publisher>
<DisplayName>Massachusetts Institute of Technology</DisplayName>
<OrgUnit />
</Publisher>
</Publishers>
<License>http://dspace.mit.edu/handle/1721.1/7582</License>
<Keyword>Physics.</Keyword>
<Abstract>This thesis presents results of two scattering studies of low dimensional magnetic materials. The first is a neutron scattering study of Rb2MnF4, a nearly ideal two-dimensional square lattice Heisenberg antiferromagnet with S = 5/2. When this material is placed in a magnetic field on an extrapolation of the spin-flop phase boundary into the paramagnetic phase, Heisenberg critical behavior can be accessed to a much longer correlation length than had previously been achieved for a high-spin system. Comparison of our results with current theories indicate that the probed temperature region lies in a crossover region from classical to renormalized classical behavior. In addition, we show measurements of both the quasielastic and magnon dynamic behavior. The second part of this thesis presents extensive synchrotron x-ray scattering measurements of the high-field incommensurate phase in doped CuGeO3. Random-field behavior, including Lorentzian-squared lineshapes, the changing of a first order transition to second-order, and critical destruction of long-range order is observed in this continuous order parameter system.</Abstract>
<Access xmlns="http://purl.org/coar/access_right"
>
</Access>
</Publication>