Perovskite bismuth ferrite is one of the most studied multiferroics since this compound can be obtained using the conventional preparation methods. BiFeO₃ is ferroelectric until T_С=1083 K, while the antiferromagnetic phase transition occurs at T_N=643 K. The temperatures of both transitions are too high and far from each other which makes difficult a beneficial use of the lattice-magnetic coupling effect.

     Recently, we initiated a systematic study of the quasi-quadruple BiFeO₃–BiScO₃–LaFeO₃–LaScO₃ perovskite system. Three end members of this system, BiFeO₃, LaFeO₃ and LaScO₃, can be obtained using the conventional methods, while a bulk perovskite BiScO₃ phase can be synthesized under the high-pressure conditions only. One of the ideas of exploration of the Bi_1-xLa_xFe_1-ySc_yO₃ system is to control the temperatures of the magnetic and the polar transitions. In this system, all the constituent cations are trivalent that makes possible to vary the parameters x and y independently. Hence, one can decrease the temperature of polar transition by means of a replacement of bismuth by lanthanum and decrease the temperature of magnetic transition through an iron-to-scandium substitution. Such substitutions were found to result in formation of new structural phases in both the as-prepared and the annealed compositions with unique combinations of polar, magnetic and elastic order parameters.