A perovskite is any material of formula ABX3 with a crystal structure similar to that of the mineral perovskite, which consists of calcium titanium oxide (CaTiO3). The mineral was first discovered in the Ural mountains of Russia by Gustav Rose in 1839 and named after Russian mineralogist L. A. Perovski (1792–1856). 'A' and 'B' are two positively charged ions (i.e. cations), often of very different sizes, and X is a negatively charged ion (an anion, frequently oxide) that bonds to both cations. The 'A' atoms are generally larger than the 'B' atoms. The ideal cubic structure has the B cation in 6-fold coordination, surrounded by an octahedron of anions, and the A cation in 12-fold cuboctahedral coordination. Additional perovskite forms may exist where both/either the A and B sites have a configuration of A1x-1A2x and/or B1y-1B2y and the X may deviate from the ideal coordination configuration as ions within the A and B sites undergo changes in their oxidation states.
A regenerative fuel cell or reverse fuel cell (RFC) is a fuel cell run in reverse mode, which consumes electricity and chemical B to produce chemical A. By definition, the process of any fuel cell could be reversed. However, a given device is usually optimized for operating in one mode and may not be built in such a way that it can be operated backwards. Standard fuel cells operated backwards generally do not make very efficient systems unless they are purpose-built to do so as with high-pressure electrolysers, regenerative fuel cells, solid-oxide electrolyser cells and unitized regenerative fuel cells.
A ferrite is one of a family of iron oxide-containing magnetic ceramic materials. They are ferrimagnetic, meaning they are attracted by magnetic fields and can be magnetized to become permanent magnets. Unlike many ferromagnetic materials, most ferrites are not electrically conductive, making them useful in applications like magnetic cores for transformers to suppress eddy currents.
Multiferroics are defined as materials that exhibit more than one of the primary ferroic properties in the same phase:
Barium titanate (BTO) is an inorganic compound with chemical formula BaTiO3. It is the barium salt of metatitanic acid. Barium titanate appears white as a powder and is transparent when prepared as large crystals. It is a ferroelectric, pyroelectric, and piezoelectric ceramic material that exhibits the photorefractive effect. It is used in capacitors, electromechanical transducers and nonlinear optics.
Bismuth ferrite (BiFeO3, also commonly referred to as BFO in materials science) is an inorganic chemical compound with perovskite structure and one of the most promising multiferroic materials. The room-temperature phase of BiFeO3 is classed as rhombohedral belonging to the space group R3c. It is synthesized in bulk and thin film form and both its antiferromagnetic (G type ordering) Néel temperature (approximately 653 K) and ferroelectric Curie temperature are well above room temperature (approximately 1100K). Ferroelectric polarization occurs along the pseudocubic direction () with a magnitude of 90–95 μC/cm2.
In its most general form, the magnetoelectric effect (ME) denotes any coupling between the magnetic and the electric properties of a material. The first example of such an effect was described by Wilhelm Röntgen in 1888, who found that a dielectric material moving through an electric field would become magnetized. A material where such a coupling is intrinsically present is called a magnetoelectric.
Cuprospinel is a mineral. Cuprospinel is an inverse spinel with the chemical formula CuFe2O4, where copper substitutes some of the iron cations in the structure. Its structure is similar to that of magnetite, Fe3O4, yet with slightly different chemical and physical properties due to the presence of copper.
In Physics, antisymmetric exchange, also known as the Dzyaloshinskii–Moriya interaction (DMI), is a contribution to the total magnetic exchange interaction between two neighboring magnetic spins, and . Quantitatively, it is a term in the Hamiltonian which can be written as
A domain wall is a term used in physics which can have similar meanings in magnetism, optics, or string theory. These phenomena can all be generically described as topological solitons which occur whenever a discrete symmetry is spontaneously broken.
The interface between lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3) is a notable materials interface because it exhibits properties not found in its constituent materials. Individually, LaAlO3 and SrTiO3 are non-magnetic insulators, yet LaAlO3/SrTiO3 interfaces can exhibit electrical metallic conductivity, superconductivity, ferromagnetism, large negative in-plane magnetoresistance, and giant persistent photoconductivity. The study of how these properties emerge at the LaAlO3/SrTiO3 interface is a growing area of research in condensed matter physics.
A complex oxide is a chemical compound that contains oxygen and at least two other elements. Complex oxide materials are notable for their wide range of magnetic and electronic properties, such as ferromagnetism, ferroelectricity, and high-temperature superconductivity. These properties often come from their strongly correlated electrons in d or f orbitals.
Nicola Ann Spaldin FRS is professor of materials science at ETH Zurich, known for her pioneering research on multiferroics.
Magnetochromism is the term applied when a chemical compound changes colour under the influence of a magnetic field. In particular the magneto-optical effects exhibited by complex mixed metal compounds are called magnetochromic when they occur in the visible region of the spectrum. Examples include K2V3O8, lithium molybdenum purple bronze Li0.9Mo6O17, and related mixed oxides. Reported magnetochromic compounds are multiferroic manganese tungsten oxide and multiferroic bismuth ferrite.
Kenji Uchino is an American electronics engineer, physicist, academic, inventor and industry executive. He is currently an academy professor of Electrical Engineering, Emeritus Academy Institute at Pennsylvania State University, where he also directs the International Center for Actuators and Transducers at Materials Research Institute. He is the former associate director at The US Office of Naval Research – Global Tokyo Office.
Julia Mundy is an American experimental condensed matter physicist. She was awarded the 2019 George E. Valley Jr. Prize by the American Physical Society (APS) for "the pico-engineering and synthesis of the first room-temperature magnetoelectric multi-ferroic material." This prize recognizes an "individual in the early stages of his or her career for an outstanding scientific contribution to physics that is deemed to have significant potential for a dramatic impact on the field." She is an assistant professor of physics at Harvard University in Cambridge, Massachusetts.
Cobalt ferrite is a semi-hard ferrite with the chemical formula of CoFe2O4 (CoO·Fe2O3). The substance can be considered as between soft and hard magnetic material and is usually classified as a semi-hard material.
Mohindar Singh Seehra is an Indian-American Physicist, academic and researcher. He is Eberly Distinguished Professor Emeritus at West Virginia University (WVU).
Europium(II) titanate is a black mixed oxide of europium and titanium, with the chemical formula of EuTiO3. It crystallizes in the perovskite structure.
Karen L. Livesey is an Australian physicist, who is an associate professor at the University of Newcastle. She was named a "Superstar of STEM" by Science Technology Australia, in the 2023–2024 cohort.
