Critical behavior of thermal diffusivity and thermal conductivity of Cr2O3 at the Néel transition

The photopyroelectric technique has been used to study the critical behavior of thermal diffusivity and thermal conductivity of Cr2O3 at the antiferromagnetic-paramagnetic phase transition. Deviation from the conventional Van Hove theory has been observed and the results have been explained in terms of a uniaxial model (n=1) with energy conservation and a nonconserved order parameter. A sharp dip, due to critical slowing down, is present in the thermal diffusivity while the thermal conductivity shows no anomaly in the critical region. A power-law fit with a background contribution and a term to correct for the thermal-diffusivity anomaly gives a critical exponent b=-0.09±0.02 and a critical amplitude ratio of U+/U-=0.51. © 1994 The American Physical Society.