Bismuth ferrite suffers from high leakage currents and the presence of a complex incommensurate spin cycloidal magnetic ordering, which has limited its commercial viability and has led researchers to investigate the functionality of doped BiFeO3 ceramics. In particular, the substitution of rare earths onto the Bi3+ site of the perovskite lattice have been shown to lead to improved functional properties, including lower leakage currents and the suppression of the magnetic spin cycloid. There is particular interest in materials with compositions close to structural morphotropic phase boundaries, because these may lead to materials with enhanced electronic and magnetic properties analogous to the highly relevant PbZrO3– PbTiO3 solid solution. However, many contradictory crystal structures and physical behaviors are reported within the literature. To understand the structure–property relationships in these materials, it is vital that we first unravel the complex structural phase diagrams. We report here a comprehensive review of structural phase transitions in rare-earth-doped bismuth ferrite ceramics across the entire lanthanide series. We attempt to rationalize the literature in terms of the perovskite tool kit and propose an updated phase diagram based on an interpretation of the literature.

Composition-driven structural phase transitions in rare-earth-doped bifeo 3 ceramics: a review

Modified ferroelectric/magnetic and leakage current density properties of Co and Sm co-doped bismuth ferrites

Theoretical investigation of magnetic, electronic and optical properties of orthorhombic YFeO3: A first-principle study

Structural, electrical and magnetic properties of rare-earth and transition element co-doped bismuth ferrites

The pure and Ho-doped Bi5Ti3FeO15 ferroelectric films with layered perovskite structure were prepared via a chemical solution deposition. One investigated the regulation of band gap and bipolar electrical cycling on photovoltaic behaviors including photovoltaic spectral response, open-circuit voltage, and short-circuit current for the films. It is shown that the photovoltaic response peak of Ho-doped Bi5Ti3FeO15 films shifts toward the visible region and the open-circuit voltage as well as short-circuit current are improved compared with the pure Bi5Ti3FeO15 films, which is attributed to the narrowed band gap after doping with Ho. And the spectral response, open-circuit voltage as well as short-circuit current of Ho-doped Bi5Ti3FeO15 films do not suffer from the fatigue like the pure Bi5Ti3FeO15 films with the action of bipolar electrical cycling. It just appears extended response peak without blue shift from the visible region. Likewise, Ho-doped Bi5Ti3FeO15 films still enjoy strong open-circuit voltage ...

Photovoltaic Behaviors Regulated by Band-Gap and Bipolar Electrical Cycling in Holmium-Doped Bi5Ti3FeO15 Ferroelectric Films

Effect of Ho3+doping on the electric, dielectric, ferromagnetic properties and TC of BiFeO3 ceramics

This paper deals with the preparation of multiferroic Bi1−x
 Ca
 x
 FeO3(x = 0–0.2) ceramics with the sol–gel method and a study on the influence of Ca2+ doping on the structure, dielectric, and ferromagnetic properties of BiFeO3 ceramics. The result shows that the XRD analysis reveals a phase transition in Ca-doped BiFeO3 from rhombohedral to orthorhombic when x is greater than 0.1. The dielectric constant (e
 r) of Bi0.9Ca0.1FeO3 measured at 1 kHz is about seven times greater than that of BiFeO3, and Bi0.8Ca0.2FeO3 is less than one-tenth of BiFeO3. It might be understood in terms of the dipole polarization, oxygen vacancy and lattice phase transition. Magnetic measurements show that the M-H of Bi1
 −
 x
 Ca
 x
 FeO3 samples exhibit unsaturated and symmetric magnetic hysteresis loops with the increase of Ca2+, indicating the weakly ferromagnetic behavior. It indicates that there is coexistence of Fe2+ and Fe3+ in Bi1
 −
 x
 Ca
 x
 FeO3 samples according to the XPS spectrum. The ratio of Fe2+/Fe3+ increases with doping Ca2+ content and the magnetic properties of BiFeO3 are enhanced. It is evident that the ferromagnetic phase transition of BiFeO3 samples occurs at 878 K by measuring the M–T and DSC curves. The T
 N of BiFeO3 will be reduced from 644 to 638 K and the T
 M does not change slightly at 878 K with increasing Ca2+ content. T
 N and T
 M of Bi1
 −
 x
 Ca
 x
 FeO3 change depends mainly on the magnetic structure of relative stability and Fe–O–Fe super-exchange strength.

Modified crystal structure, dielectric properties, and magnetic phase transition temperature of Ca doped BiFeO3 ceramic

Ferroelectric field-effect transistors (Fe-FET) are promising candidates for future information devices. However, they suffer from low endurance and short retention time, which retards the application of processing memory in the same physical processes. Here, inspired by the ferroelectric proximity effects, we design a reconfigurable two-dimensional (2D) MoS2 transistor featuring with asymmetric ferroelectric gate, exhibiting high memory and logic ability with a program/erase ratio of over 106 and a self-rectifying ratio of 103. Interestingly, the robust electric and optic cycling are obtained with a large switching ratio of 106 and nine distinct resistance states upon optical excitation with excellent nonvolatile characteristics. Meanwhile, the operation of memory mimics the synapse behavior in response to light spikes with different intensity and number. This design realizes an integration of robust processing memory in one single device, which demonstrates a considerable potential of an asymmetric ferroelectric gate in the development of Fe-FETs for logic processing and nonvolatile memory applications.

Asymmetric Ferroelectric-Gated Two-Dimensional Transistor Integrating Self-Rectifying Photoelectric Memory and Artificial Synapse.

Effects of trivalent gadolinium and cobalt co-substitution on the crystal structure, electronic transport, and ferromagnetic properties of bismuth ferrite

In this work we report experimental evidence for the weak high-temperature ferromagnetism in Bi1-xRxFeO3 (R = Dy, Y) compounds by careful characterizations, excluding the possible side-effects from other iron-based impurities. Remarkable saturated magnetic moment was observed in the Y-substituted samples, Bi1-xYxFeO3, which is larger than the moment obtained in Bi1-xDyxFeO3, the Dy-substituted samples with antiferromagnetic background. The physical origin of the weak ferromagnetic transition is discussed and serious lattice distortions have been identified based on the X-ray diffraction and Raman scattering data, although the rhombohedral structure symmetry remains unchanged upon the substitutions. It is believed that the structural distortion suppressed cycloid spin structure is the main factor for the enhanced magnetization in Bi1-xRxFeO3 compounds. Additionally, the Dy3+-Fe3+ antiferromagnetic coupling, which strengthens the antiferromagnetic interaction in Bi1-xDyxFeO3 compounds, acts as the driving force for the magnetic discrepancy between Bi1-xYxFeO3 and Bi1-xDyxFeO3 samples.

Jian Su

Papers

Effect of Ho3+doping on the electric, dielectric, ferromagnetic properties and TC of BiFeO3 ceramics

Modified crystal structure, dielectric properties, and magnetic phase transition temperature of Ca doped BiFeO3 ceramic

Asymmetric Ferroelectric-Gated Two-Dimensional Transistor Integrating Self-Rectifying Photoelectric Memory and Artificial Synapse.

Effects of trivalent gadolinium and cobalt co-substitution on the crystal structure, electronic transport, and ferromagnetic properties of bismuth ferrite

Enhanced high temperature ferromagnetism in Bi 1-x R x FeO 3 (R = Dy, Y) compounds.