Neutron Diffraction Experiment on a Randomly Mixed Antiferromagnet with Competing Spin Anisotropies

抄録

Neutron diffraction experiment has been done on a randomly mixed antiferromagnet with competing spin anisotropies, Fe_(1−x)Co_xCl₂. Front the experiment the spin structures in the three ordered phases which appear in the concentration versus transition temperature phase diagram, namely, the Fe-rich and Co-rich antiferromagnetic phases and the new phase are determined. The spin structure in the Fe-rich (Co-rich) phase is essentially identical with that of pure FeCl₂ (CoCl₂). In the new phase, although overall spin structure is the same as those of the pure materials, both of the two spin components are observed which are associated with competing anisotropies. The new phase is an OAF phase in the sense that an inclination of the sublattice magnetizations both from the easy axes of the pure substances means the simultaneous ordering of the spin components. The temperature dependences, of the spin components are discussed in favour of the result of the renormalization group theory.