Group of magneto-optical investigations 2
Members of the group:
Kharchenko M.F., Head of the group, Proffesssor, Doctor of Sciences (Dr.Sc.), Academician of NAS of Ukraine, leading researcher.
Myloslavskaya O.V., Candidate of Sciences (Ph.D), researcher;
Lukienko I.M., junior researcher;
Kharchenko Yu.M., junior researcher;
Tutakina O.I., engineer.
The main field of research:
Studies of properties of antiferromagnetic crystals that are asymmetric with respect to inversion and anti-inversion operations by magneto-optical and magnetic methods.
Magneto-optical spectroscopy investigations ofproperties of magnetic nanostructures including one-dimensional magnetic photonic crystals, multilayered nanofilms ferromagnet/normal metal, hydro-oxide layered structures with transition metal 3d ions.
Optical visualization of 180-degree antiferromagnetic domains, studying the possibilities of their switching and creation.
Investigation by optical and magnetooptic spectroscopy methods of structural transformations in Jahn-Teller crystals in a magnetic field.
Equipment:
Equipment for magnetooptic spectroscopic investigations (birefringence, dichroism) in the Voight and Faraday experimental geometries: magnetic field – up to 7 T; spectral range – 300 - 800 nm; temperature range – 6 - 300 K; frequency of piezo-acoustic modulator – 18 kHz.
Equipment for visual observations of magnetic, antiferromagnetic and crystalline domain structures in the static magnetic field up to 7 T in the temperature range 6 - 300 K.
Equipment for measurements of the Faraday, polar and longitudinal Kerr effects: magnetic field up to 1.7 T, room temperature.
The most important results:
The linear magneto-optical effect in the incommensurate magnetic phase of the known antiferromagnetic magnetolelectric LiNiPO4 was revealed which evidences the loss of the crystal symmetry at the transition from a paramagnetic to a modulated antiferromagnetic state of symmetry relative to a combined space-time inversion operation.
It has been shown experimentally that in double-layer microresonator photonic crystals based on a bismuth-substituted iron-yttrium garnet a record increase in the magneto-optical Faraday effect is observed, this material demonstrating and have well-defined advantages over other types of magnetic photonic crystal.
The low-temperature properties of microresonator magnetic photonic crystals, the magnetic-active layer of which has a magnetic compensation temperature, have been investigated for the first time, and it has been shown that under strong temperature changes of magnetoopic properties of defect layers, the resonance wavelength does not change within thousandths parts. The results can be used when creating magnetic photonic crystals with temperature-sensitive properties.
Anomalies of magnetoresistive and magneto-optical properties of ferro-magnetic/normal metal [Co/Cu]n multilayer nanofilms observed at certain thicknesses of layers of normal metal have been detected experimentally and it is shown that they are accompanied by nanostructuring of ferromagnetic metal layers caused by the indirect influence of spatial electronic quantization in copper layers on the structure of cobalt layers.
For the first time, the behavior of hydrogen bonds in Co-containing double layered hydroxides [Ñî2+1-xAl3+x(OH)2]x+(COy-3)x/y·5H2O has been investigated using low-temperature optical spectroscopic and polarization methods. The effect of "freezing" hydrogen bonds has been revealed and it is concluded that hydroxides having the highest concentration of cobalt cations are most promising for the creation of practically important hydroxides by anion exchange.
International cooperation:
Institute of Physics of the Polish Academy of Sciences (IP PAN), Warsawa, Poland;
Universidade de Aveiro (CICECO), Aveiro, Portugal;
University of Geneva (UNIGE), Geneva, Switzerland.