The Ferroic Phase Transitions of BiFeO₃

Abstract

BiFeO3 displays an abrupt first order transition from the polar structure R3c to centrosymmetric $R\bar 3c$ at TC = 830 °C. The ferroelectric transition is associated with abrupt changes in polar cation displacements and a large discontinuous volume. A continuous volume expansion occurs across the second order antiferromagnetic transition at TN = 370 °C. Electronic conductivity anomalies are associated with both phase transitions.

Phase transition and enhanced magneto-dielectric response in BiFeO3-DyMnO3 multiferroics

“…1(b) in log scale. 5 Therefore, the R3c space group has been selected to refine the crystal structure up to x ¼ 0.075. The intensity magnitude of the superlattice peak (113) reflection decreases with increase in x.…”

“…[1][2][3][4][5][6][7][8][9][10][11] An essential feature of a multiferroic system is the presence of magnetoelectric (ME) coupling (not all multiferroics are magnetoelectric, e.g., BaCoF 4 ) which permits a mutual control between ferroic order parameters (i.e., electric and magnetic ordering). 2,11 Multiferroics are very rare in nature due to the chemical incompatibility and mutual exclusiveness of ferroelectric and ferromagnetic ordering in many oxides, more common among fluorides.…”

“…4 The ferroelectricity in BFO is caused by the Bi 6s lone pair electrons, while spin of transition metal cation Fe 3þ is responsible for G-type antiferromagnetic ordering with a long range spin cycloid with period of 620-640 Å . 4,5 Recent experimental investigations on BFO outline the major inherent issues, which should still be addressed: (a) synthesis of stoichiometric compound, (b) high leakage current and dielectric loss, and (c) weak magneto-electric coupling. [1][2][3][4][5] The ferroelectric phase transition temperature is much higher than the AFM Neel temperature (i.e., Type-I multiferroic), and a weak magneto-electric coupling is observed.…”

“…4,5 Recent experimental investigations on BFO outline the major inherent issues, which should still be addressed: (a) synthesis of stoichiometric compound, (b) high leakage current and dielectric loss, and (c) weak magneto-electric coupling. [1][2][3][4][5] The ferroelectric phase transition temperature is much higher than the AFM Neel temperature (i.e., Type-I multiferroic), and a weak magneto-electric coupling is observed. The origin of the problems mentioned above warrants further investigation.…”

Magnetoelectric Ordering of BiFeO3 from the Perspective of Crystal Chemistry

“…Nevertheless, there is still no agreement among the researchers on the transition temperature and symmetry of the paraelectric -phase. The crystal structure of the -phase has been identified as rhombohedral c R3 in [28], tetragonal in [29], cubic mcm I / 4 m Pm3 in [30], monoclinic m P 1 2 or m C 2 in [31], and, recently, as orthorhombic Pbnm in [32]. The change of structure, loss of magnetic order and metallization of BiFeO 3 are also observed under pressure of [45][46][47][48][49][50][51][52][53][54][55] GPa at room temperature [33][34][35][36].…”