The thermal conductivity of NiO and CoO at the Neel temperature

Abstract
The thermal conductivity of singly crystals of NiO has been measured in the temperature range 100-650K and that of CoO in the range 100-450K, both ranges including the Neel temperature. Sharp minima at the magnetic transition are qualitatively explained in terms of Stern's theory of the critical scattering of phonons by the spin system. Data are also reported on the specific heat and electrical resistivity of the crystals around the magnetic transition, the former showing critical behaviour which is very similar to that found in many other ordered systems. There is evidence from the latter of a divergence in the rate of change of resistivity with temperature, behaviour so far reported only in magnetic metals.