ANNA RYKOVA
E-mail: rykova@ilt.kharkov.ua
Phone.: +(380) 57 341 0975
Affiliation and address
B.Verkin Institute for Low Temperature Physics
& Engineering, National Academy of Sciences of Ukraine,
47 Lenin Ave., 61103 Kharkov, Ukraine
Date of birth: 02.06.1981
Place of birth: Kharkov,Ukraine
Education
1. Kharkov State University. Diploma of Physics & Mathematics. 2003.
Career/Employers
B.Verkin Institute for Low Temperature Physics and Engineering,
Kharkov.
2003 - 2006 – postgraduate student
2006 - till now – a junior researcher
Specialization
main field: magnetism of low symmetric and low dimensional system;
current research interest: static and dynamic magnetic characteristics of strongly anisotropic magnetic insulators with magnetic ions of rare-earth and transition metals (in magnetically ordered and paramagnetic states); phase transitions and relaxation processes in this type of compounds; investigation of nonstationary and nonlinear phenomena.
Professional skills:
measurments of magnetic characteristics of materials (magnetization and magnetic susceptibility) using different methods (induction methods, vibration magnetometer in a wide range of temperatures, magnetic fields and frequencies), operation of cryogenic equipment (4He, 3He pumped cryostats).
Publications
Number of paper on refereed journals more than 4
Number of communication to scientific meetings more than 26
Main Publications
1. E.N.Khatsko, A.S.Cherny, A.I.Rykova, M.T.Borowiec, H.Szymchak, V.P.Dyakonov. Low-temperature magnetic properties of the monoclinic magnet RbDy(WO4)2. Low Temperature Physics, 29, 1009, 2003.
The temperature dependence of the magnetic susceptibility of RbDy(WO4)2 was measured. Strong anisotropy of the susceptibility is observed. At TN=0.8 K the phase transition to a magnetically ordered state is found. The field dependence of the magnetization at T=0.5 K demonstrates a metamagnetic phase transition. Structural phase transitions was observed at temperatures around 5,8 and 50 K.
2. K.Dergachev, M.Kobets, A.Rykova, E.Khatsko. ESR investigation of monoclinic singlet KTb(WO4)2. Proceedings of the 20th General Conference of Condensed Matter Division of EPS, Prague, 2004, Book of Abstracts, p. 175.
KTb(WO4)2 refers to the monoclinic space group 2C/c. In the range of temperatures 1.8-300 K the crystal is paramagnetic. High frequency properties of KTb(WO4)2 was studied at temperatures 1.7-4.2 K in frequency range 1.8-120 GHZ. The energy gaps between lowest electron levels and g-factors of the ground state was determined. When external field is applied perpendicular to chains direction a structural phase transition induced by magnetic field was detected. Phase transition is going through the incommensurate phase.
3. E.N.Khatsko, M.Kobets, K.Dergachev, A.Rykova. Resonant investigation of a Low-Dimensional Monoclinic NaFe(WO4)2. Proceedings of Conference Modern Development of Magnetic Resonance, Kazan, 2004.
Low-dimensional monoclinic compound NaFe(WO4)2 was investigated by resonant methods. Frequency-field dependences of AFMR indicate this compound as two-axes low-dimensional antifferomagnet. Characteristic parameters of energy spectrum of AFMR was defined, such as: energy gaps, anisotropy fields, and exchange field. Relation between intra- and inter-plane exchange was estimated. Additional absorption which is connected with local modes was detected.
4. E. Khatsko, A.Loginov, A. Cherny, A.Rykova, Magnetic properties of strongly correlated chain antiferromagnet KTb(WO4)2, Physica B 378-380, (2006), 1126-1127.
The susceptibility and magnetization of single crystal of KTb(WO4)2 has been measured in the temperature range 0.5–80 K in magnetic fields up to 6T. It is shown that KTb(WO4)2 is an Ising magnet with only one component of the magnetic moment. The three-dimensional phase transition to the antiferromagnetically ordered state has been found below 0.7 K. This transition can be described in the molecular field two-level approximation. The principal exchange constant has been estimated. By using experimental data the magnetic structure of KTb(WO4)2 is proposed.
5. A. I. Rykova, A. S. Cherny , E. N. Khatsko, A. D. Shevchenko, and V. N. Uvarov, Magnetic properties of
p-La0.78Mn0.99O3.5 and p-La0.80Mn1.04O3.5 obtained at high pressure 7.5 GPa, Low Temperature Physics, 34, 918, 2008.
Structural and magnetic studies of nanocomposite samples of lanthanum manganite p-La0.78Mn0.99O3+δ and p-La0.80Mn1.04O3+δ with excess oxygen (δ=0.5) have been performed. The samples were obtained at high pressure (7.5 GPa). X-Ray studies showed that the samples consist of a single phase and possess perovskite cubic structure. The lattice parameters were determined. Scanning atomic-force microscopy was used to find the characteristic sizes of the nanograins (70 nm). Temperature studies of the magnetic susceptibility showed that at temperature of the order of 260 K both samples pass into the ferromagnetic state. Above TC the samples exhibited paramagnetic behavior and follow the Curie–Weiss law χ=C/(T-θ) with a positive Curie–Weiss constant θ ≈ 280 ± 1 K for both samples. Below TC the nanocomposites exhibited spin-glass behavior. However, the field dependences of the magnetization of the samples differed substantially. The saturation fields for p-La0.78Mn0.99O3.5 and p-La0.80Mn1.04O3.5 differed by a factor of 4, and a strong temperature dependence of the magnetic rigidity was observed for both compounds. The effective magnetic moments for p-La0.78Mn0.99O3.5 and p-La0.80Mn1.04O3.5 are 0.84µB and 3.24µB.