Magnetic Order in the Heavy Fermion CompoundCeCu6at mK Temperatures

Abstract

We have measured the ac magnetic susceptibility in various fields and thermal expansion of single crystals of the heavy fermion compound ${\mathrm{CeCu}}_6$ at temperatures down to $250\mu \mathrm{K}$. The susceptibility of ${\mathrm{CeCu}}_6$ shows a peak at about 2 mK and has a large anisotropy. We also detected an anomaly of thermal expansion at the same temperature. The observed behaviors of the susceptibility and the thermal expansion in ${\mathrm{CeCu}}_6$ indicate the occurrence of an antiferromagnetic order.