A NEW-TYPE OF SPIN ORDERING IN A RANDOM MAGNET WITH COMPETING ANISOTROPIES

The result of an elastic neutron-scattering study of the phase transit ion in the random magnet with competing anisotropies Fe0.75Co0.25Br2 i s reported. It was found that the ordering of the spin component paral lel to the crystalline c axis at the transition from the paramagnetic to antiferromagnetic phase induces an ordering of the spin component p erpendicular to it. Thus, there is no boundary separating the higher-t emperature antiferromagnetic and lower-temperature mixed-ordering phas e. This type of spin ordering is interpreted as arising from a couplin g between the orthogonal spin components.