Isotropic State in a Random Mixture of Two Anisotropic Antiferromagnets

Susceptibility measurements have been done on a random mixture of two anisotropic antiferromagnets with different orientations of easy axes, FeCl 2 ·2H 2 O and CoCl 2 ·2H 2 O. An isotropic state in which the anisotropy in the susceptibility becomes zero is found in the intermediate concentration region. A preliminary specific heat measurement suggests that the isotropic state lies within an ordered phase of the random mixture. The present experiment is discussed in connection with the existing theory.