Bi1−xRxFeO3 (R=rare earth): a family of novel magnetoelectrics

Abstract Crystals of solid solutions Bi 1− x R x FeO 3 , where R =La, Dy, Gd, were obtained with χ ⩽0.7. Solid solutions of the stated rare earths, as χ is increased from 0 to 0.7, have one and the same sequence of five crystal structures (rhombohedral C 6 3v , triclinic C 1 1 , orthorhombic D 6 2 , orthorhombic D 5 2 , orthorhombic C 9 2v ). The ferroelectric-paraelectric transition occurs in rhombohedral and triclinic crystals at T =810−560° C . The high temoerature modifications are orthorhombic and cubic. The orthorhombic structure C 9 2v holds up to 1180°C. The ferroelectric domain structure was distinguished in all types of crystals. No magnetoelectric effect (MEE) was detected in the orthorhombic crystals with the D 2 (222) symmetry class. But the mm2 crystals were found to have both quadratic and linear MEE. The value of the quadratic effect is considerably smaller than that of the linear one. Magnetoelectric hysteresis takes place in the crystals. The tensorial properties of the obtained crystals are analyzed from the viewpoint of crystal symmetry.