Single-phase Bi 1−x Nd x FeO 3 ͑BNFO x ͒ ͑x =0-0.2͒ multiferroic ceramics were prepared to study the effects of Nd substitution on their crystal structure and ferroelectromagnetic behavior. Rietveld refinement of x-ray diffraction data showed a continual transformation of crystal structure from the rhombohedral structure of BNFO x=0 ͑BiFeO 3 ͒ to a triclinic structure in BNFO x=0.05-0.15 and a pseudotetragonal structure in BNFO x=0.175-0.2. Ferroelectromagnetic measurements revealed the existence of ferroelectricity with remnant polarization of ϳ9 C/cm 2 in BNFO x=0-0.175 , paraelectricity in BNFO x=0.2 , and weak ferromagnetism with remnant magnetizations of 0.07-0.227 emu/ g in BNFO x=0.15-0.2. Magnetoelectric coupling was obvious in BNFO x=0.15-0.175 near the Néel temperature of ϳ380°C.

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Single-phase and lead-free Bi 0.85 La 0.15 FeO 3 multiferroic ceramics were prepared by a rapid liquid sintering method to study their crystal structure and multiferroic behaviors. Rietveld refinement of X-ray diffraction data showed a pseudo-cubic structure plus a small triclinic distortion. The absence of Fe 21 ions suggested few oxygen vacancies. Large polarizations of 20.3 lC/cm 2 together with a piezoelectric d 33 coefficient of B27.7 pC/N were achieved. This ferroelectricity originates from the stereochemical activity of the A-site Bi 31 lone electron pair. The remnant magnetizations of 0.0744-0.227 emu/g of Bi 0.85 La 0.15-FeO 3 permitted by the canting angle of canted antiferromagnetic order was released as a result of the collapse of the spacemodulated spin structure of BiFeO 3 . The observed dielectric anomalies proved the magnetoelectric couplings between ferroelectric order and canted antiferromagnetic order. J ournal

Bi 0.825 Nd 0.175 Fe O 3 (BNFO) thin film is grown on Pt∕TiO2∕SiO2∕Si substrate by pulsed laser deposition, and its multiferroic properties are compared with those of BiFeO3 (BFO) thin film. With limited Fe2+ ions and its twinborn oxygen vacancies, both samples show low dielectric losses of <0.026 at 100Hz and high maximum ferroelectric polarizations of ∼34μC∕cm2. The ferroelectric coercive field of BNFO is reduced by ∼40%, reaching a low value of 235kV∕cm, compared to that of BFO due to the increased ratio of 180° and curved ferroelectric domains to total ferroelectric domains and better nucleation of the ferroelectric domains at the BNFO∕Pt interface. The Raman scattering spectra confirm that the ferroelectric polarizations of both samples originate in the stereochemical activity of the Bi lone electron pair. Weak ferromagnetism is observed in both samples as a result of the limited amount of Fe2+ ions and γ-Fe2O3 impurity.

Polycrystalline Sr2Fe1−xAlxMoO6 compounds with x=0, 0.05, 0.10, 0.15, and 0.30 were fabricated and their low-field magnetoresistance (LFMR) performance studied. The LFMR was greatly enhanced as x increased from nil to 0.15, and its origin was found to be intragranular spin-dependent scattering. The replacement of Fe by Al weakened the antiferromagnetic exchange in the antiphase boundary arising from the antisite defect and acted as a barrier for electron transport along the Mo–O–Fe–O–Mo–O–Fe chain in the ferromagnetic segregation and weakened the ferromagnetic exchange. When the external magnetic field was applied, the spin in the antiphase boundary appeared to align more easily to the external field after Al doping and the transport of the electron was easier due to the weakening of the double exchange barrier.

A Monte Carlo algorithm based on the hybrid Ising-DIFFOUR model is proposed to investigate the phase transition in ferroelectromagnetic lattice in which the ferroelectric order and antiferromagnetic order coexist below a certain temperature. The Ising spin moment and ferroelectric displacement and their susceptibilities as well, as a function of temperature for systems of different magnetoelectric couplings, are simulated and compared with the mean-field approach. The typical antiferromagnetic transition at Néel point and the ferroelectric transition at Curie point are observed at zero coupling. It is demonstrated that a weak ferromagnetic order can be activated by introducing the magnetoelectric coupling or applying external magnetic field, while the external electric field has little effect on the ferromagnetic ordering behavior.

The temperature-dependent dielectric and ferroelectric fatigue behaviors of ABO3-type perovskite thin films Pb(Zr0.52Ti0.48)O3 (PZT) and Pb0.75La0.25TiO3 (PLT) and layered Aurivillius thin films SrBi2Ta2O9 (SBT) and Bi3.25La0.75Ti3O12 (BLT) with Pt electrodes are studied. The improved fatigue resistance of PZT and PLT at a low temperature can be explained by the defect-induced suppression of domain switch/nucleation near the film/electrode interface, which requires a long-range diffusion of defects and charges. It is argued that the fatigue effect of SBT and BLT is attributed to the competition between domain-wall pinning and depinning. The perovskitelike slabs and/or (Bi2O2)2+ layers act as barriers for long-range diffusion of defects and charges, resulting in localization of the defects and charges. Thus, the fatigued SBT and BLT can be easily rejuvenated by a high electric field over a wide temperature range.

Thin films of A-site substituted, B-site substituted, and both A- and B-sites cosubstituted Bi4Ti3O12 (BTO) by La3+ and Zr4+, i.e., Bi3.25La0.75Ti3O12 (BLT), Bi4Ti2.8Zr0.2O12 (BTZ), and Bi3.25La0.75Ti2.8Zr0.2O12 (BLTZ), were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. Structures of the films are investigated by x-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Compared to the well known BLT films, both the BTZ and BLTZ films have larger remanent polarization (Pr) but smaller coercive field (Ec). It is shown experimentally that the oxygen vacancy is the predominant factor determining ferroelectric fatigue. The effects of substitution on structural and ferroelectric properties of BTO are discussed in detail. As a result, the A- and B-sites cosubstitution might be one of the promising ways to improve ferroelectric properties of BTO.