Publication Date

2015-04-30

Availability

Open access

Embargo Period

2016-04-29

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Physics (Arts and Sciences)

Date of Defense

2015-04-02

First Committee Member

Joshua L. Cohn

Second Committee Member

Fulin Zuo

Third Committee Member

Sunxiang Huang

Fourth Committee Member

Francisco M. Raymo

Abstract

Experimental measurements of heat conduction in the low-dimensional antiferromagnetic compounds CuSb2O6 and BiCu2PO6 are presented for the range 0.5K≤T≤390K. Both compounds have magnetic exchange ( J) and Debye (θ_D) energies that are comparable. This distinguishes the present work from prior studies which have focused on the regime J≫θ_D. Individual crystals were characterized by x-ray diffraction to identify bicrystallinity, twinning and other defects. Thermal conductivity κ(T) for both the spin-½ chain compound (CuSb2O6) and the spin-½ two-leg ladder compound (BiCu2PO6) imply strong spin-phonon resonant scattering. Model fitting to the lattice component of the heat conductivity was employed to extract a characteristic energy scale for the magnetic excitations. Anisotropy was evident in κ of both compounds, possibly associated with heat conduction by the spin system. The magnetic mean free path inferred from the data are also presented and compared with those of other low-D spin systems.

Keywords

Spin-Phonon coupling; Quantum magnets; heat transport; thermal conductivity; Antiferromagnetic; Low dimensional

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