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TbxEr1−xNi5compounds: An ideal model system for competing Ising-XYanisotropy energies
Pirogov, A. N.,Park, J.-G.,Ermolenko, A. S.,Korolev, A. V.,Kuchin, A. G.,Lee, Seongsu,Choi, Y. N.,Park, Junghwan,Ranot, Mahipal,Yi, Junghwan,Gerasimov, E. G.,Dorofeev, Yu. A.,Vokhmyanin, A. P.,Podlesn American Physical Society 2009 Physical review. B, Condensed matter and materials Vol.79 No.17
Magnetism of ordered and disordered alloys of R<sub>2</sub>Fe<sub>14</sub>B (R=Nd, Er) type
Teplykh, A.E.,Chukalkin, Yu.G.,Lee, S.,Bogdanov, S.G.,Kudrevatykh, N.V.,Rosenfeld, E.V.,Skryabin, Yu.N.,Choi, Y.,Andreev, A.V.,Pirogov, A.N. Elsevier Sequoia 2013 Journal of alloys and compounds Vol.581 No.-
Magnetic susceptibility, magnetization and neutron diffraction measurements have been performed to study structure and magnetic states of crystalline and amorphous Nd<SUB>2</SUB>Fe<SUB>14</SUB>B and Er<SUB>2</SUB>Fe<SUB>14</SUB>B alloys. In the crystalline state there exists a large (about 20%) anisotropy of Er-sublattice magnetization. Values of the magnetic anisotropy constant of Er ions and the Er-Fe exchange-coupling parameter were estimated using temperature dependence of the Er- and Fe-sublattice magnetizations. Amorphous state of the samples was obtained by irradiation of fast (E<SUB>eff</SUB>≥1@?eV) neutrons with a fluence up to the 1.2x10<SUP>20</SUP>n/@?m<SUP>-2</SUP> at 340K. It is shown that antiferromagnetic coupling between the rare-earth and iron spins is kept in the amorphous state. Amorphization of the samples is found to result in reduction of the Curie temperature (T<SUB>C</SUB>) by about 200K and almost total absence of coercivity. We suggest that the strong decrease of T<SUB>C</SUB> is a consequence of enhancement of negative Fe-Fe interactions as a result of dispersion of interatomic distances, which is a characteristic feature of the amorphous state.
Chepurnov S.A.,Chepurnova N.E.,Jin-Kyu Park,Redkozubova O.M.,Pravdukhina A.A.,Abbasova K.R.,Buzinova E.V.,Mirina A.A.,Chepurnova D.A.,Dubina A.A.,Pirogov U.A.,Curtis M.,Uva L. 고려인삼학회 2007 Journal of Ginseng Research Vol.31 No.3
Pharmacology of Korean Red ginseng gives us unique possibility to develop new class of antiepileptic drugs today and to improve one’s biological activity. The chemical structures of ginsenosides (GS) have some principal differences from well-known antiepileptic new generation drugs. The antiepileptic effect of GS was also demonstrated in all models of epilepsy in rats (young and adult), which have studied, in all models of epilepsy including status epilepticus (SE), induced by lithium - pilocarpine. In our experiments in rats new evidences on protective effects were exerted as a result of premedication by GS. Pre-treatment of several GS could induce decrease of the seizures severity and brain structural damage (by MRI), neuronal degeneration in hippocampus. Wave nature of severity of motor seizures during convulsive SE was observed during lithium-pilocarpine model of SE in rats (the first increase of seizures was 30 min after the beginning of SE and the second - 90 min after. The efficacy of treatment on SE by ginsenoside as expected was observed after no less 3 weeks by daily GS i.p. administration. It is blocked SE or significantly decrease the severity of seizures during SE. The implication of presented data is that combination of ginsenosides from Korean Red ginseng and ginseng cell culture Dan25 that could be applied for prevention of epileptical status development. However, a development of optimal ratio of different ginsenosides (Rb1 Rc, Rg, Rf,) should consummate in the new antiepileptic drug development.
Effects of magnetic anisotropy and exchange in Tm2Fe17
Pirogov, A. N.,Bogdanov, S. G.,Rosenfeld, E. V.,Park, J. -G.,Choi, Y. N.,Lee, Seongsu,Prokeš,, K.,Golosova, N. O.,Sashin, I. L.,Kudrevatykh, N. V.,Skryabin, Yu. N.,Vokhmyanin, A. P. Pleiades Publishing 2012 Journal of experimental and theoretical physics Vol.115 No.5
Determination of Texture Degree of NdFeB-Magnets by Means of Neutron Diffraction
Teplykh, A.E.,Bogdanov, S.G.,Choi, Yong,Kudrevatykh, Nikolai V.,Pirogov, A.N.,Popov, A.G.,Skryabin, Yu.N.,Vyatkin, V.P. Trans Tech Publications, Ltd. 2010 Diffusion and defect data. SSP. [Pt. B], Solid sta Vol.168 No.-
<P>Six samples of Nd-Fe-B-permanent magnets, distinguished in the texture degree, have been measured by neutron diffraction in the reflection and transmission regimes. The texture in the samples was formed by application of impulses of external magnetic field 0H = 4 T. Analysis of the obtained neutron diagrams by means of the Fullprof program allowed quantitative determination of the texture degree and conclusion to be made that the texture degree grows with an increase in numbers of magnetic field impulses.</P>
Urusova, N.,Semkin, M.,Kratochvilova, M.,Barykina, J.,Volegov, A.,Park, J.-G.,Lee, S.,Pirogov, A. Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.781 No.-
<P><B>Abstract</B></P> <P>Lithium orthophosphates of the Li<I>M</I>PO<SUB>4</SUB> type (<I>M</I> = Ni, Co, Fe, and Mn) gain intensive development due to the potential applications as electrodes for lithium-ion batteries. The other remarkable property of Li<I>M</I>PO<SUB>4</SUB> is the multiferroicity. We present a study of the crystal structure and magnetic properties, refined anisotropic thermal coefficients and Li-ion migration maps of the LiNi<SUB>0.9</SUB> <I>M</I> <SUB>0.1</SUB>PO<SUB>4</SUB> (<I>M</I> = Co, Mn) single crystals and compared results for the undoped LiNiPO<SUB>4</SUB> and LiMnPO<SUB>4</SUB> ones. All samples have been synthesized by the flux method. In LiNi<SUB>0.9</SUB> <I>M</I> <SUB>0.1</SUB>PO<SUB>4</SUB> (<I>M</I> = Co, Mn), doping increases the lattice constants, unit cell volume, valence bonds, and the anisotropic thermal coefficients. By means of X-ray diffraction and the program package TOPOS, the Li-cation migration maps were obtained. The Li-ions move along the [010] direction which can be clearly visualized in the mixed-metal LiNi<SUB>0.9</SUB> <I>M</I> <SUB>0.1</SUB>PO<SUB>4</SUB> (<I>M</I> = Co, Mn) single crystals. It was found that the 10% doping of LiNiPO<SUB>4</SUB> by cobalt ions leads to a decrease in the formation temperature and to the suppression of the incommensurate phase. The 10% doping of manganese ions increases the transition temperature, while the temperature range of the incommensurate phase narrows.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Structure of Li<I>M</I>PO<SUB>4</SUB> has been refined using single crystal X-ray diffractometer. </LI> <LI> Using Voronoi–Dirichlet approach, the Li-ion migration map was obtained. </LI> <LI> The magnetic phase transition temperatures of Li<I>M</I>PO<SUB>4</SUB> single crystals were determined. </LI> <LI> Co- and Mn-doped LiNiPO<SUB>4</SUB> leads to suppression of the incommensurate phase. </LI> </UL> </P>
Chukalkin, Yu.G.,Teplykh, A.E.,Kudrevatykh, N.V.,Choo, K.N.,Lee, S.,Andreev, A.V.,Pirogov, A.N. Elsevier 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.615 No.-
<P><B>Abstract</B></P> <P>Magnetization and neutron diffraction measurements have been carried out to study evolution of structure and magnetic states of amorphous Nd<SUB>2</SUB>Fe<SUB>14</SUB>B and Er<SUB>2</SUB>Fe<SUB>14</SUB>B alloys under isothermal annealing at 295–1025K. The amorphization have been performed by neutron irradiation which provides a homogeneous state in different with other methods of amorphization. The annealing induces a rise of α-Fe phase content in alloys and a recrystallization into Nd<SUB>2</SUB>Fe<SUB>14</SUB>B-type phase. Neutron diffraction data show that the recrystallization occurs over narrow temperature interval (590–638) K in Er<SUB>2</SUB>Fe<SUB>14</SUB>B and at around 800K in Nd<SUB>2</SUB>Fe<SUB>14</SUB>B. Magnetic measurements testify that in both samples the magnetization and coercive field increase with annealing temperature above 800K.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Annealing of R<SUB>2</SUB>Fe<SUB>14</SUB>B amorphized by fast neutrons. </LI> <LI> Annealing leads to crystallization above 600 K (R = Er) and 800 K (R = Nd). </LI> <LI> Crystallization is accompanied by increase of magnetization and coertivity. </LI> </UL> </P>