Tetracritical behaviours of random mixtures with competing spin anisotropies

Abstract

A tetracritical behaviour has clearly been observed in a random mixture of two antiferromagnets with competing spin anisotropies, FeCl 2 · 2 H 2 O and CoCl 2 · 2 H 2 O. A neutron diffraction experiment and Mössbauer spectroscopy on the mixture have demonstrated that the new phase observed in the intermediate concentration region is the mixed ordering phase, or equivalently the oblique antiferromagnetic phase. Experimental work on another mixture with competing spin anisotropies, Fe (1−x)Co xCl 2, is also reported.