Multiferroic thin films with the general formula $\mathrm{Bi}{\mathrm{Fe}}_{1-x}{\mathrm{Sc}}_x{\mathrm{O}}_3$ ($x=0.0$ , 0.1, 0.3, and $0.5\mathrm{mol}\%$ ) (BFS) were synthesized on $\mathrm{Pt}∕\mathrm{Ti}∕\mathrm{Si}{\mathrm{O}}_2∕\mathrm{Si}$ substrates through a sol-gel deposition method. From the x-ray diffraction (XRD) analysis, it was observed that the unit cell volume increased upon Sc doping up to $0.3\mathrm{mol}\%$ . Impure phase appeared for the BFS (Sc: $0.5\mathrm{mol}\%$ ) films. Leakage current, ferroelectric, and magnetic properties were also found to improve for Sc doping up to $0.3\mathrm{mol}\%$ . Room temperature magnetic coercive field for in-plane orientation of films showed the lowest value for BFS (Sc: $0.3\mathrm{mol}\%$ ) films, which indicates that BFS (Sc: $0.3\mathrm{mol}\%$ ) films were more magnetically soft. Room temperature value of the magnetodielectric effect in the presence of magnetic field of $8\mathrm{kOe}$ was found to have maximum of 3.36% for the BFS (Sc: $0.3\mathrm{mol}\%$ ) films. From the x-ray photoelectron spectroscopy measurements, it was observed that the Fe has mixed valency states of $2+$ and $3+$ . The ratio of ${\mathrm{Fe}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ was found to decrease slightly in BFS (Sc: $0.3\mathrm{mol}\%$ ) films. The improved leakage current and $M\text{-}H$ loops support the authors’ observation.

We present a systematic and detailed study of the magnetization reversal process and magnetotransport properties of ${\mathrm{Fe}}_3{\mathrm{O}}_4∕\mathrm{Cu}$ $\left(t_{\mathrm{Cu}}\right)∕{\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ spin valve structures. A drastic change was observed in both the magnetic and transport properties as the thickness of the Cu spacer layer $t_{\mathrm{Cu}}$ was varied in the range $2\mathrm{nm}⩽t_{\mathrm{Cu}}⩽30\mathrm{nm}$. For $t_{\mathrm{Cu}}=2\mathrm{nm}$, the transport properties are mainly due to anisotropic magnetoresistance effects because of strong exchange coupling between the ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ and ${\mathrm{Fe}}_3{\mathrm{O}}_4$ layers. For $t_{\mathrm{Cu}}⩾5\mathrm{nm}$, however, the transport properties are dominated by positive giant magnetoresistance (GMR) effects due to separate magnetization switching of the two magnetic layers. The GMR ratio decreases with increasing spacer layer thickness due to enhanced current shunting and scattering effects. We also observed that the GMR ratio has strong temperature dependence and decreases with increasing temperature due to spin flip scattering and electron-magnon interactions.

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.

The effect of Ti substitution on the microwave and magnetostatic properties of nanostructured hexagonal BaFe_12−xTi_xO₁₉ ferrite composites is studied. The microwave permeability is measured in the frequency range of 0.1–22 GHz by a coaxial technique. An analysis of the magnetostatic data is made by the law of approach to saturation. The ferrimagnetic resonance frequencies calculated from the magnetostatic data are consistent with those obtained from the microwave measurements. The natural ferrimagnetic resonance frequencies are located in the frequency range of 15 to 22 GHz, depending on the substitution level x. An increase in the amount of substitution elements results in a low-frequency shift of the ferrimagnetic resonance frequency for samples with x < 1. With x rising from 1 to 2.5, the resonance frequency increases. The results of the study demonstrate that the tailored optimization of the nano-structure of a functional material is a robust tool to fine-tune its microwave magnetic properties. The ferrites under study are promising materials to be applied as functional coatings intended to control electromagnetic interference in microwave devices.

Potassium sodium niobate (KNN) is a lead free ceramic that can potentially replace PZT (Pb(ZrTi)O₃). However, KNN suffers from a few major disadvantages. These include the presence of highly volatile alkaline elements and stoichiometry sensitive properties coupled with severe difficulties in controlling the composition. In this work, La doped sodium potassium niobate based perovskite (ABO₃) ceramics, more specifically [{(1-x)(K_0.5Na_0.5)xLa}Nb_(1–2x/5)O₃] (0 < x < 0.1), have been developed. Among these, the material at 5 mol. % La doping appears with an unusually high density up to 99% of its theoretical value, while densities of the parent K_0.5N_0.5NbO₃ (KNN) ceramics typically only reach ∼70% to 89% of the theoretical limit. The developed ceramics in their circular and rectangular disk form with thickness 0.8 mm show transparency and most importantly, this transparency is electrically tunable up to 52%. Additionally, the material shows sensitivity of its magnetic and optical properties to ultraviolet (UV) irradiation, i.e., these materials transform to a metastable and reversible state that exhibits graded color change from clear to deep blue and shows a considerable increase in magnetization under UV exposure. This feature makes the developed ceramics attractive for the fabrication of new generation devices; e.g., powerless UV detectors as well as protectors, since it absorbs UV completely. Based on first-principles calculations, we developed a model that attributes these observations to the occupancy of La f_xyz orbitals induced by UV excitations. The model also indicates that UV induced absorption in the visible range and magnetism are related.