SPIN REORIENTATION IN MIXED SAMARIUM-DYSPROSIUM ORTHOFERRITES

Flux-grown single crystals of solid solutions of the rare-earth orthoferrites SmFeO3 and DyFeO3 have been studied from 2° to 500°K. At elevated temperatures all compositions have iron moments antiferromagnetically aligned along [100] and slightly canted toward [001]. In SmFeO3 and all but the Dy-rich mixtures a transition (a-c reorientation) to antiferromagnetic alignment along [001] with canting toward [100] occurs at temperatures decreasing from about 450°K for SmFeO 3 to below 30°K at 80 at.% Dy. DyFeO3 and the Dy-rich mixtures undergo an a-b reorientation to antiferromagnetic alignment of the iron spins along [010] with no overt canting. The temperature at which the ferromagnetic moment vanishes decreases from about 30°K for DyFeO 3 to about 15°K at 15 at.% Sm. Both types of transition occur gradually over well defined temperature intervals, and are believed to be associated with temperature variation of the second order anisotropy coefficients of the iron spins. The phenomenological theories proposed to describe the a-c reorientation are extended to include the a-b reorientation also, and stability conditions for the three spin arrangements are deduced. © 1969 The American Institute of Physics.