There is a correlation between the structure and magnetic properties of ceramics

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.

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). CREDIT Vadim Sikolenko
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). CREDIT Vadim Sikolenko

A group from the Research and Educational Center “Functional Nanomaterials” of Immanuel Kant Baltic Federal University (BFU) together with an international scientific group considered a connection between’s the structure of ceramic materials dependent on bismuth ferrite (BiFeO3) and their magnetic properties.

In their work, the researchers hypothetically justified the acquired outcomes and decided the variables that influence the auxiliary development of materials and changes in their magnetic behavior. The work will help make new ceramic materials with given properties.

The structure of bismuth ferrite is like that of perovskite, a calcium, and titanium-based mineral, yet in addition, contains oxygen atoms. Well-known high-temperature superconductors (i.e. materials ready to conduct the current without opposition at specific temperatures) have a similar structure. Numerous materials with perovskite-like crystal grids are utilized as solar energy processors.

At the point when particles of various components are added to source bismuth ferrite, it prompts changes in its crystal grid and in this manner in physical properties. Scientists included particles of metals (calcium, manganese, titanium, and niobium) to it and estimated the material’s magnetic characterstics. It worked out that the inclusion of new atoms prompts the pressure of the crystal lattice cross section paying little mind to the sort of the transitional components.

This, thus, is trailed by changes in the material’s magnetic structure. It loses unconstrained polarization, i.e. dipole moments of the atoms (that decide the course of electric powers) are denied of fixed introduction without an outside electric field. At the point when particles of different metals are added to bismuth ferrite, the last additionally loses its ferromagnetic properties: dipole snapshots of iotas are never again coordinated towards one another.

Also, when calcium is included with niobium or titanium, the magnetic structure of the material transforms into ferromagnetic: the dipole minutes moved toward becoming codirectional. After the impact of magnetic field stopped, these samples showed residual magnetism, a property typical for ferromagnetic materials.

Vadim Sikolenko, a co-author of the work, candidate of physics and mathematics said, “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.”

The article of the scientists was published in the Journal of Physics and Chemistry of Solids.