Anisotropic thermal conductivity of CuO
- Akopyan, A.
- Prasai, N.
- Rebello, A.
- Neumeier, J. J. [ Montana State University: Physics ]
- Cohn, J. L.
We report measurements of the low-temperature (5K T 300 K) thermal conductivity (kappa) of single-crystal CuO along its main symmetry directions. The influence of the antiferromagnetic phase transitions (TN1 213 K, TN2 230 K) on kappa is modest. The application of an electric field (<= 6 kV/cm) in the multiferroic regime (TN1 T TN2) was explored but found to produce no measurable effect on kappa attributable to a manipulation of magnetic domains. In the collinear ground state, there is considerable anisotropy of kappa, with substantially larger values along ([101]) and transverse to ([101]) the CuO chains for which superexchange interactions are strongest. Calculations of the lattice thermal conductivity employing the measured anisotropic phonon dispersions satisfactorily reproduce the conductivities in all but the [101] and [101] directions, suggesting a substantial magnon contribution (kappa m) along the latter. A model employing the measured spin-wave dispersions and anisotropic spin gap produces reasonable agreement with the inferred kappa m(T ).