Alicia Huang

Mutual ferromagnetic-ferroelectric coupling in multiferroic copper-doped ZnO.

A mutual ferromagnetic and ferroelectric coupling (multiferroic behavior) in Cu‐doped ZnO is demonstrated via deterministic control of Cu doping and defect engineering. The coexistence of multivalence Cu ions and oxygen vacancies is important to multiferroic behaviors in ZnO:Cu. The samples show clear ferroelectric and ferromagnetic domain patterns. These domain structures may be written reversibly via electric and magnetic bias.

Improved magnetoelectric coupling in Mn and Zn doped CoFe2O4–PbZr0.52Ti0.48O3 particulate composite

In this letter, Mn and Zn simultaneously substituted CoFe2O4, Co0.6Zn0.4Fe1.7Mn0.3O4 has been proposed as magnetostrictive component having the maximum in plane piezomagnetic coupling coefficient (q11+q12∼0.070 ppm/Oe) at a field of H∼300 Oe with appreciable saturation values of longitudinal and transverse magnetostriction coefficients (λ11∼−20 ppm and λ12∼10 ppm). On incorporating this in composite (i.e., (x) PbZr0.52Ti0.48O3−(1−x) Co0.6Zn0.4Fe1.7Mn0.3O4) preparation, maximum magnetoelectric voltage coefficients (αE∼122 mV/cm Oe) was obtained in sample x=0.90 at ac magnetic field of amplitude ∼1 Oe and frequency ∼1 kHz.

Hydrothermal synthesis of (00l) epitaxial BiFeO3 films on SrTiO3 substrate

Epitaxial thin films of multiferroic BiFeO3 (BFO) are successfully grown on (100) SrTiO3 substrates using a hydrothermal synthesis method at 120–200 °C in a relatively short time of 2–8 h. It is found that the morphology evolution of the (001)PC-oriented BFO films over time and temperature involve unique dissolution–reprecipitation reactions, whereby initial large sparse islands dissolve, and re-precipitate into dense mosaic-like structures that further grow vertically, resembling those of terrace-like structures. High-resolution transmission electron microscopy (HRTEM) and ψ-ω-2θ high resolution thin film X-ray diffraction scans suggest that the BFO films have relaxed to a monoclinic structure—different from the rhombohedral bulk BFO powders. Peak fittings of the powders and films reveal that the lattice parameters contract when either reaction time or temperature is increased. Similar lattice contraction is also observed when the films/powder are annealed at 550 °C in N2 atmosphere for 10 min. Dielectric constant and loss, leakage current and ferroelectric properties of the BFO film improve with annealing, attributed to a reduced amount of defects.

STRESS ANALYSIS OF (001) PREFERRED ORIENTED BiFeO3 AND Bi(Cr0.03Fe0.97)O3 FILMS

ABSTRACT Comparative stress analysis of (001)-preferred oriented BiFeO3 (BFO) and Bi(Cr0.03Fe0.97)O3 (BCF) films formed by the chemical solution deposition method on LaAlO3 and La0.27Sr0.73Ta0.35AlO3 substrates, using high resolution X-ray diffraction (HRXRD), sin2ψ method, micro-Raman and high resolution transmission electron microscopy (HRTEM) was carried out. Tensile stresses are found in all films compared to the compressive stresses measured by HRTEM. Compressive stresses occur at the interface due to lattice mismatch between the substrates and BFO/BCF. The BFO films contained higher tensile stresses ∼8.57 GPa than the BCF films ∼5.20 GPa. Intrinsic stresses played a larger factor in the residual stress of the films.