Dilution Studies of Multiferroic ReFeO$_{3}$ with Bi

BiFeO$_{3}$ possesses simultaneous ferroelectric (T$_{c}$ = 1100 K) and antiferromagnetic (T$_{N}$ = 640 K) order but weak coupling between the states. The Fe moments in DyFeO$_{3 }$order at T$_{N}$ = 645 K and the Dy spins order below 4K, accompanied by an induced ferroelectric state. We study the interplay between Dy multiferroism in DyFeO$_{3 }$and Bi ferroelectricity in BiFeO$_{3 }$by measuring the magnetization of single crystals of the solid solution series (Dy,Bi)FeO$_{3}$. We find, for a limited range of Bi concentrations, an anomalous increase in the Dy ferromagnetic Curie temperature and cancellation of ferromagnetism on the Dy and Fe sublattices. We also study the effects of Bi substitution in ReFeO$_{3}$ for Re = Sm, Gd, Er, and Tm.