Multiferroic magnetoelectric composite systems such as ferromagnetic-ferroelectric heterostructures have recently attracted an ever-increasing interest and provoked a great number of research activities, driven by profound physics from coupling between ferroelectric and magnetic orders, as well as potential applications in novel multifunctional devices, such as sensors, transducers, memories, and spintronics. In this Review, we try to summarize what remarkable progress in multiferroic magnetoelectric composite systems has been achieved in most recent few years, with emphasis on thin films; and to describe unsolved issues and new device applications which can be controlled both electrically and magnetically.

Recent Progress in Multiferroic Magnetoelectric Composites: from Bulk to Thin Films

An insight into the analogies, state-of-the-art technologies, concepts, and prospects under the umbrella of perovskite materials (both inorganic-organic hybrid halide perovskites and ferroelectric perovskites) for future multifunctional energy conversion and storage devices is provided. Often, these are considered entirely different branches of research; however, considering them simultaneously and holistically can provide several new opportunities. Recent advancements have highlighted the potential of hybrid perovskites for high-efficiency solar cells. The intrinsic polar properties of these materials, including the potential for ferroelectricity, provide additional possibilities for simultaneously exploiting several energy conversion mechanisms such as the piezoelectric, pyroelectric, and thermoelectric effect and electrical energy storage. The presence of these phenomena can support the performance of perovskite solar cells. The energy conversion using these effects (piezo-, pyro-, and thermoelectric effect) can also be enhanced by a change in the light intensity. Thus, there lies a range of possibilities for tuning the structural, electronic, optical, and magnetic properties of perovskites to simultaneously harvest energy using more than one mechanism to realize an improved efficiency. This requires a basic understanding of concepts, mechanisms, corresponding material properties, and the underlying physics involved with these effects.

Mutual Insight on Ferroelectrics and Hybrid Halide Perovskites: A Platform for Future Multifunctional Energy Conversion.

Magnetocaloric effect: From materials research to refrigeration devices

A2B′B″O6 perovskites: A review

Electrocaloric materials for future solid-state refrigeration technologies

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)(K0.5Na0.5)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 K0.5N0.5NbO3 (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 fxyz orbitals induced by UV excitations. The model also indicates that UV induced absorption in the visible range and magnetism are related.

Lead-free perovskite ceramics with ultraviolet-tunable optical and magnetic properties at room temperature

BaTiO3 (BT) and Ni0.5Zn0.5Fe2O4 (NZF) ceramic disc specimens were prepared using commercial grade powders sintering by conventional (CV) and microwave (MW) sintering techniques. In both the sintering techniques the set sintering temperatures were in the range of 850 °C to 1000 °C and time from 0.5 to 2 h. Structure, microstructure, dielectric, ferroelectric and magnetic properties have been compared for the as sintered BT and NZF ceramic specimens. Comparatively large grain size and higher density observed for the samples sintered at same temperature and shorter holding time using microwave. Magnetic properties of the NZF samples sintered using MW at a temperature of 950 °C show a higher saturation magnetization (Ms) value of 88 emu/g.

https://www.mdpi.com/2227-7080/3/1/47/pdf

Comparison of Grain Structure, Electrical and Magnetic Properties of BaTiO3 and Ni0.5Zn0.5Fe2O4 Ceramics Sintered Using Microwave and Conventional Techniques

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.

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

Publisher's Note: “Ferroelectric capped magnetization in multiferroic PZT/LSMO tunnel junctions” [Appl. Phys. Lett. 106, 132901 (2015)]

PROBLEM TO BE SOLVED: To provide a method and apparatus for manufacturing a piezo-electric film structure for MEMS element that is protected enough from failure and/or contamination in the manufacturing process of the piezo-electric film. SOLUTION: The MEMS element includes a substrate provided with a first plane, a second plane opposite to the first plane, and a space formed between the first plane and the second plane, and a first piezo-electric thin film structure formed on the first plane of the substrate and a second piezo-electric thin film structure formed on the second plane of the substrate. COPYRIGHT: (C)2010,JPO&INPIT

Santiranjan Shannigrahi

Papers

Lead-free perovskite ceramics with ultraviolet-tunable optical and magnetic properties at room temperature

Comparison of Grain Structure, Electrical and Magnetic Properties of BaTiO3 and Ni0.5Zn0.5Fe2O4 Ceramics Sintered Using Microwave and Conventional Techniques

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

Publisher's Note: “Ferroelectric capped magnetization in multiferroic PZT/LSMO tunnel junctions” [Appl. Phys. Lett. 106, 132901 (2015)]

Fine processing electro-mechanical element