Denis Vinnik, Doctor of Sciences (Chemistry), Professor, Head of the Department of Material Science and Physical Chemistry of Materials, Director of the Research Institute for Advanced Materials and Resource-Saving Technologies at SUSU. Credit: SUSU.
The study
of complex oxides of iron to create new functional materials is one of the most
intensely developing fields of investigation for SUSU scientists. The physical
properties of complex iron oxide systems can be varied by changing the chemical
composition. This makes it possible to trace the fundamental effects that arise
when ions are replaced. In a new study, researchers chose to investigate
spinel-structured ferrites, changing their magnetic properties through
modification of their chemical composition by substituting iron ions. The
results of their research were published in Nanomaterials.
The
researchers, an international group including scientists from SUSU and their
colleagues from Belarus, Saudi Arabia and India examined ferrites of the Co-Ni
system with double substitution of iron ions by thulium and terbium ions. The
chemists were interested in the magnetic properties of the investigated
compounds that manifest themselves in ferrites during the transition to the
nanoscale.
During the
study, the scientists established the peculiarities of the distribution of
substituted ions in the structure of ferrite spinel. The relevance of the study
was due to the correlation between the distribution of the substituent ions in
the ferrite spinel and its influence on the magnetic properties under
conditions of double substitution of iron ions by Tm and Tb ions comparable in
radius.
"The
samples were synthesized via the sol-gel method, which allows for the creation
of nanoscale complex oxides. However, ultrasonic assistance was applied during
the synthesis, which allowed us to achieve a more homogeneous distribution of
substituting ions and to reduce the average size of the crystallites,"
said SUSU chemist Dr. Denis Vinnik.
The
synthesis was carried out by scientists from Saudi Arabia. The study of
microstructural parameters and magnetic properties of nanosized ferrite spinels
was carried out at the SUSU Nanotechnology Research and Education Centre. As a
result, specialists identified an interesting feature of the oxides under
study: With the increase in the degree of substitution of iron ions by ions
with large radii, the unit cell parameter decreased, although theoretically, it
should have increased.
"We
suggested that this anomaly could be the result of the effect of surface
compression of nanocrystallites. Thus, the decrease in the crystallite size
resulting from substitution by Tm and Tb ions led to an increase in the surface
layer fraction. This, as we know, can lead to the effect of surface compression
in nanoscale crystallites, and as a consequence, the deformation of the unit
cell," said Aleksey Trukhanov, senior researcher of the SUSU
Nanotechnology Research and Education Centre.
For now,
the studies are theoretical, but they can be used as a foundation to complete
further studies on the synthetization of compounds of complex iron oxides and
correction of their properties. The scientists' plans include studying the
functional properties of ferrite spinels in absorbing electromagnetic
radiation.
The
scientists noted that the chemical compounds can be used in electronics for the
creation of sensors as well as in biomedicine for targeted delivery of
medicines or contrast visualization.