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

Abstract

Crystals of solid solutions Bi1 _~R~FeO3, where R= La, Dy, Gd, were obtained with x~0.7. Solid solutions of the stated rare earths, as xis increased from 0 to 0.7, have one and the same sequence of five crystal structures (rhombohedral~triclinic C{, orthorhombic D~,orthorhombic Dl, orthorhombic Ct). The ferroelectric-paraelectric transition occurs in rhombohedral and triclinic crystals at T= 810-560°C.The high temperature modifications are orthorhombic and cubic. The orthorhombic structurẽ 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 D2 (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 ofthe linear one. Magnetoelectric hysteresis takes place in the crystals. The tensorial properties of the obtained crystals are analyzed from the viewpoint of crystal symmetry.

Physics and Applications of Bismuth Ferrite

“…[74] The nature of the intermediate bridging phases, however, is unclear. Gabbasova et al [86] and Zalesskii et al [87] claim a noncentric orthorhombic phase (C222) for 0.2 < x < 0.6 that could also be associated with the hightemperature b phase of pure BiFeO 3 -the sudden volume contraction at x ¼ 0.2 is in this context very reminiscent of the volume contraction observed at the temperature-induced a-b transition (825 8C). At any rate, the exact nature and even the number of structural phase transitions as a function of La doping is still an open question.…”

“…At any rate, the exact nature and even the number of structural phase transitions as a function of La doping is still an open question. [63,[86][87][88] 2.5. Other Anomalies above Room Temperature: Phase Transitions vs.…”

Phase transitions in multiferroic BiFeO3crystals, thin-layers, and ceramics: enduring potential for a single phase, room-temperature magnetoelectric ‘holy grail’

“…The introduction of rare-earth substituents can thus change the anisotropy constant, so that the presence of spatially modulated structures would be energetically unfavorable. The first experiments of this type were done in the late 1980s -early 1990s on crystals of Bi 1-x R x FeO 3 (R =La, Gd, Dy) for 0.4<x<0.5 [67][68][69], which revealed the presence of a linear ME effect up to liquid nitrogen temperatures, as shown in Figure 10a. The high magnetic field measurements showed that the presence of lanthanum additives x~0.1 reduces the transition field from the spatially modulated state to homogenous [70,71].…”

Magnetic Topological Structures in Multiferroics

“…In order to release LME it is necessary to suppress cycloid. It can be achieved by rare earth ions doping [5], action of high magnetic fields [6,9]. High magnetic fields induce the transition from cycloidal state into uniform antiferromagnetic phase that is accompanied by essential increase of electric polarization indicating LME (Fig.…”