UBC Theses and Dissertations

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UBC Theses and Dissertations

We have nothing to lose but our spin chains Horton, Matthew D. P.

Abstract

Two quantum spin chains problems are discussed. Firstly, using the exact form factors of the 0(3) nonlinear a model the three-magnon contribution to the spin correlation function of a spin-1 chain is calculated. A very broad peak with a small amplitude is predicted. The integrated intensity of this contribution relative to the single magnon peak is of the order 2%. Experimentally, such a contribution would be difficult, if not impossible, to observe. In the second problem we consider the problem of doping spin-1 magnetic materials with nonmagnetic impurities. In the case where interchain coupling is weak, the nonmagnetic impurities effectively cut decoupled spin chains into finite lengths. We impose free boundary conditions at the chain ends and apply bosonization, mapping the problem onto a torus. Using this formalism we are able to numerically calculate the alternating susceptibility for any reasonable length chain at any temperature. The Neel temperature is then calculated for a three dimensional square lattice as a function of average chain length.

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