Multiferroic bismuth ferrite-based materials for multifunctional applications: Ceramic bulks, thin films and nanostructures

BiFeO3, the paradigm of single-phase multiferroic materials, has potential applications in information storage, sensors and actuators This perovskite has a rhombohedral R3c crystallographic structure and shows a spin-modulated cycloidal magnetic structure with a modulation period of ∼62 nm It reveals magnetoelectric coupling at room temperature However, its low remanent magnetization and relatively important leakage current are the main limitations for possible applications In this review we summarize recent studies on doped BiFeO3 Special attention is put on obtaining and sintering bulk BiFeO3 ceramics and the effect of doping on the electric and magnetic properties

BiFeO3: A review on synthesis, doping and crystal structure

Effect of Eu substitution on the crystal structure and multiferroic properties of BiFeO3

Raman spectra, supplemented by powder x-ray diffraction and magnetization data of isovalently A- and B-site substituted BiFeO3 in the Bi1−xLaxFeO3 (0≤x≤1), Bi1−xTbxFeO3 (0≤x≤0.2), and Bi0.9Sm0.1Fe1−xMnxO3 (0≤x≤0.3) series, are presented. A good agreement between the structural transitions observed by x-ray diffraction and the vibrational modes observed in the Raman spectra is found over the whole substitutional ranges, and in particular we find spectroscopic signatures of a PbZrO3-type structure for Bi0.8La0.2FeO3. Mode assignments in the substituted materials are made based on Raman spectra of the end-members BiFeO3 and LaFeO3. Moreover, by comparing spectra from all samples with R3c structure, the phonon assignment in BiFeO3 is revisited. A close connection between the degree of octahedral tilt and the Raman shift of the A1 oxygen a−a−a− tilt mode is established. An explanation for the strong second-order scattering observed in Bi1−xLaxFeO3 and Bi1−xTbxFeO3 is suggested, including the assignment of the previously mysterious BiFeO3 mode at 620 cm−1. Finally, the magnetization data indicates a transition from a cycloidal modulated state towards a canted antiferromagnet with increasing A-site substitution, while Bi0.9Sm0.1Fe1−xMnxO3 with x=0 and 0.15 exhibit an anomalous closing of the hysteresis loop at low temperatures. For low A-site substitution levels (x≤0.1) the decreasing Raman intensity of the Fe derived modes correlates with the partial destruction of the spin cycloid as the substitution level increases.

https://publications.lib.chalmers.se/records/fulltext/167824/local_167824.pdf

Structural and magnetic properties of isovalently substituted multiferroic BiFeO3: Insights from Raman spectroscopy

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

We report on magnetization and magnetocapacitance measurements in the ${\text{Bi}}_{1\ensuremath{-}x}{\text{La}}_{x}{\text{FeO}}_{3}$ series for $0\ensuremath{\le}x\ensuremath{\le}0.15$. We confirm that doping with La reduces the threshold magnetic field ${H}_{\text{c}}$ for cancelling the magnetic spiral phase, and we show that ${H}_{\text{c}}$ decreases as the La content increases up to $x=0.15$, which is the highest concentration for maintaining the noncentrosymmetric rhombohedral structure of ${\text{BiFeO}}_{3}$. Measurements of the dielectric constant as a function of magnetic field in the series also show a maximum magnetocapacitance for $x=0.15$.

Magnetization and magnetoelectric effect in Bi 1-x La x FeO 3 (0≤x≤0.15)

We have performed magnetization and magnetocapacitance measurements on ceramic samples of the multiferroic series Bi 1− x La x FeO 3 for 0≤ x ≤.0.25. We show that doping with La reduces the transition magnetic field from the spatially modulated state to a homogenous one and increases the magnetocapacitance, these effects being the strongest for x =0.15, which is the highest concentration for maintaining the non-centrosymmetric rhomboedral structure (R3c) of BiFeO 3 . For highest La content ( x ≥0.17), analysis of the XRD patterns shows that the lattice symmetry gradually changes to orthorhombic (C222), giving rise to an enhancement of the latent magnetization and to a drop of the magnetodielectric constant.

Effect of La doping in the multiferroic compound BiFeO3

We have used 170Yb Mossbauer spectroscopy on Yb3+ diluted at the Y3+ sites to study YBa2(Cu0.94Zn0.06)3Ox. In the fully oxygenated sample, the presence of Zn2+ introduces a Korringa dependence of the Yb3+ paramagnetic relaxation rate, indicating an increase in the density of states at the Fermi level, which is visible both above and below Tc (32 K). A molecular field coming from the Cu (2) is observed on all the Yb3+ probes in non-superconducting samples with x = 6.0 and 6.5 showing that at these oxygen levels, all the Cu (2)'s are locally magnetically correlated. For x = 6.88 molecular fields suggesting there is phase separation between local magnetic and non-magnetic superconducting regions. For x = 7.0, none of the Cu(2)'s are magnetically correlated. The general features of the oxygen-level dependence of the local magnetic properties are similar in the zinc-substituted and in the zinc-free samples, but magnetic ordering persists to higher oxygen levels when Zn2+ is present.

Magnetic properties of YB2(Cu0.94Zn0.06)3Ox (x = 6.0 to 7.0) studied by Mössbauer spectroscopy on substituted 170Yb3+

The Ni ({S} = 1) chain compound Yb2BaNiO5 (space group: Immm) is the end magnetic member of the isomorphous rare earth series We have studied its magnetic properties using 170Yb Mossbauer spectroscopy and neutron diffraction Magnetic order is induced into the Ni2+ chains through the polarization of the Yb3+ and leads to an ordering temperature of 88 K The Ni2+ moments, saturated value 11 µB, are antiferromagnetically aligned close to the c-axis and the Yb3+ moments, saturated value 06 µB, are antiferromagnetically aligned at an angle of 55° to the c-axis and close to the (ac) plane The thermal evolution of the Yb3+ moment is well described with a phenomenological molecular-field model The value derived for the effective polarizing field acting on the Ni2+ when expressed per Yb3+ moment is much higher than the equivalent value for any of the other rare earths

170Yb Mössbauer and neutron diffraction measurements on spin-chain Yb2BaNiO5

We report on magnetisation and magneto-capacitance measurements in the Bi1-xLaxFeO3 series for 0 < x < 0.15. We confirm that doping with La reduces the threshold magnetic field Hc for cancelling the magnetic spiral phase, and we show that Hc decreases as the La content increases up to x=0.15, which is the highest concentration for maintaining the non-centrosymmetric rhombohedral structure of BiFeO3. Measurements of the dielectric constant as a function of magnetic field in the series also show a maximum magneto-capacitance for x=0.15.

N. Genand-Riondet

Papers

Magnetization and magnetoelectric effect in Bi 1-x La x FeO 3 (0≤x≤0.15)

Effect of La doping in the multiferroic compound BiFeO3

Magnetic properties of YB2(Cu0.94Zn0.06)3Ox (x = 6.0 to 7.0) studied by Mössbauer spectroscopy on substituted 170Yb3+

170Yb Mössbauer and neutron diffraction measurements on spin-chain Yb2BaNiO5

Magnetization and magneto-electric effect in La-doped BiFeO3