We have investigated the thermal conductivity (k) and magnetoresistance (MR) of non-doped and hole-doped delafossite CuCrO2 with a spin-3/2 antiferromagnetic (AF) triangular sublattice. The phonon mean free path above the Néel temperature (TN) deduced from k and lattice specific heat is almost identical to the magnetic correlation length, which indicates that, for both compounds, spin fluctuation enhanced in a geometrically frustrated lattice is strongly coupled with acoustic phonon above TN. k below TN is significantly suppressed by Mg substitution, suggesting the introduction of some disorder into the 120° Néel state. For the hole-doped CuCr0.97Mg0.03O2, a negative MR is observed above TN, which is enhanced with a decrease in T toward TN, while a component of positive MR appears below T N and the residual negative MR component is observed in a high magnetic field, indicating that spin fluctuation coupled with electrical conductivity is critically enhanced above TN and remains below T N. These results evidence that the 120° Néel state is partially disordered by a doped itinerant hole coupled with spin fluctuation, although AF transition is certainly promoted. The dynamic partial disorder may stabilize the Néel order through an order-bydisorder mechanism.
- Antiferromagnetic triangular lattice
- Thermal conductivity
ASJC Scopus subject areas
- Physics and Astronomy(all)