Quasi-one-dimensional magnetism in TiOCl and a theory of a lightly doped dimerized insulator

Transition metal oxides with low dimensional geometry have displayed fascinating new phenomena such as high temperature superconductivity and unconventional magnetism. The first part of this thesis is related to this rich and diverse subject, where TiOCl is studied as an example of an S = 1/2 layered Mott insulator. Earlier experiments on this material indicating two-dimensional spin-liquid behavior are reviewed critically and are compared to new susceptibility data. The latter suggest a new picture, where band structure effects produce quasi-one-dimensional spin chains formed by t2g orbitals. Based on these findings, TiOC1 is proposed to be a new example of Heisenberg-chains which undergo a spin-Peierls transition. Within this picture, the effect of doping with non-magnetic Sc impurities can be explained in good agreement with the experiment. The magnetic energy scale of J - 660K and the frustration of the interchain geometry render TiOC1 unique among materials with a spin-Peierls transition. This unusual geometry is interpreted as the main reason for the failure of conventional mean-field theory to describe the details of the transition such as its first order character. It will be shown that a simple Ginzburg-Landau theory which takes proper account of interchain-frustration is capable of explaining this unconventional behavior.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Seidel, Alexander, 1975-

Advisor dc:contributor.advisor

• Patrick A. Lee.

• Physics.

Statement dc:rights

• 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.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/17013

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/17013