A team from Baltic Federal University (BFU) together with an international scientific group studied a correlation between the structure of ceramic materials based on bismuth ferrite (BiFeO3) and their magnetic properties
A team from the Research and Educational Center "Functional Nanomaterials" of Immanuel Kant Baltic Federal University (BFU) together with an international scientific group studied a correlation between the structure of ceramic materials based on bismuth ferrite (BiFeO3) and their magnetic properties.
This is an electronic microscope image showing the coexistence of two phases -- a rhombohedral and an orthorhombic one --- in a multiferroic. On the right: calculated Fourier density of electronic states for each of the two phases at different temperatures (the image has been taken at room temperature).
Source: Vadim Sikolenko
In their work the scientists theoretically justified the obtained results and determined the factors that affect structural evolution of materials and changes in their magnetic behavior. The work will help create new ceramic materials with given properties. The article of the scientists was published in the Journal of Physics and Chemistry of Solids.
The structure of bismuth ferrite is similar to that of perovskite, a calcium and titanium-based mineral, but also contains oxygen atoms. Well-known high-temperature superconductors (i.e. materials able to conduct the current without resistance at certain temperatures) have the same structure. Many materials with perovskite-like crystal grids are used as solar energy processors.
When ions of different elements are added to source bismuth ferrite, it leads to changes in its crystal lattice and therefore in physical properties. BFU physicists added ions of metals (calcium, manganese, titanium, and niobium) to it and measured the material's magnetic characteristics. It turned out that the insertion of new atoms leads to the compression of the crystal lattice regardless of the type of the transitional elements.
This, in turn, is followed by changes in the material's magnetic structure. It loses spontaneous polarization, i.e. dipole moments of the atoms (that determine the direction of electric forces) are deprived of fixed orientation in the absence of an external electric field.
When atoms of other metals are added to bismuth ferrite, the latter also loses its ferromagnetic properties: dipole moments of atoms are no longer directed towards each other. Moreover, when calcium is added together with niobium or titanium, the magnetic structure of the material turns into ferromagnetic: the dipole moments became codirectional. After the influence of a magnetic field stopped, these samples showed residual magnetism, a property typical for ferromagnetic materials.
"We've demonstrated that the magnetic properties of bismuth ferrite-based materials are to a great extent determined by structural distortions caused by substitutions, lattice defects, and the nature of exchange interaction between the atoms of iron, oxygen, and the transitional metal.
Weak ferromagnetic states that occurred when calcium was added to the material together with titanium or niobium, are explained by the reaction between magnetic atoms that goes through the non-magnetic ones.
Usually, it is not taken into account due to its minor values, but in case of ferromagnetic materials it may cause considerable fluctuations in the magnetic behavior of the material," says Vadim Sikolenko, a co-author of the work, candidate of physics and mathematics, and senior researcher at the Research and Educational Center "Functional Nanomaterials".
The work was carried out in cooperation with scientists from MIET National Research University, Science and Practical Center for Material Studies of the National Academy of Sciences of Belarus, I.M. Sechenov First Moscow State Medical University, Joint Institute for Nuclear Research, University of Coimbra (Portugal), and University of Lodz (Poland).
Julia Shkurkina | EurekAlert!
The taming of the light screw
22.03.2019 | Max-Planck-Institut für Struktur und Dynamik der Materie
21.03.2019 | Max-Planck-Institut für Polymerforschung
DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.
The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...
Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.
The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...
Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.
Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...
The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.
A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...
Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.
"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...
11.03.2019 | Event News
01.03.2019 | Event News
28.02.2019 | Event News
22.03.2019 | Life Sciences
22.03.2019 | Life Sciences
22.03.2019 | Information Technology