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Irreversible field-induced magnetic phase transitions and properties of Ho<sub>3</sub>Co
Baranov, N V,Goto, T,Hilscher, G,Markin, P E,Michor, H,Mushnikov, N V,Park, J-G,Yermakov, A A IOP Pub 2005 Journal of physics, an Institute of Physics journa Vol.17 No.21
<P>The results of magnetic susceptibility, magnetization, electrical resistivity and specific heat measurements performed on Ho<SUB>3</SUB>Co single crystals show that this compound exhibits two different antiferromagnetic structures: AF<SUB>II</SUB> at 8 K<<I>T</I>< 22 K and AF<SUB>I</SUB> below <I>T</I><SUB>t</SUB>≈8 K. Below the Néel temperature <I>T</I><SUB>N</SUB> = 22 K the application of a magnetic field along the main crystallographic directions induces magnetic phase transitions which are accompanied by giant magnetoresistance. At <I>T</I><<I>T</I><SUB>t</SUB> the field-induced phase transitions along the <B><I>c</I></B>- and <B><I>b</I></B>-axes are found to be irreversible, and a small ferromagnetic component is observed along the <B><I>a</I></B>-axis. These peculiarities are associated with the non-Kramers character of the Ho ion and with the presence of a complex incommensurate magnetic structure of Ho<SUB>3</SUB>Co below <I>T</I><SUB>N</SUB>. The temperature coefficient of the electrical resistivity for Ho<SUB>3</SUB>Co above <I>T</I><SUB>N</SUB> over a wide temperature range is found to differ from that observed for other R<SUB>3</SUB>Co compounds. Such a behaviour is attributed to the presence of an additional contribution to the conduction electron scattering by spin fluctuations induced by f–d exchange in the itinerant d-electron subsystem. The value of this extra contribution and its temperature range is suggested to depend on the spin value of the R ion. The excess of the effective magnetic moment per R ion, which is observed in Ho<SUB>3</SUB>Co and in other R<SUB>3</SUB>M type compounds, is also attributed to spin fluctuations induced by f–d exchange.</P>
Luminescent Properties of ZnO/MgO Nanocrystal/Polymer Composite Structure
Gennady N. Panin,Andrey N. Baranov,Irina A. Khotina,Tae W. Kang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
We report on cathodoluminescence (CL) studies of the composite nanostructure obtained by spin coating of a mixture of chemically-deposited ZnO/MgO nanocrystals and a solution processable polymer (PDPV) on a Si substrate with patterned gold electrodes. The effect of an electric field on the CL of the nanostructure was studied at various bias voltages on the electrodes. A positive voltage suppressed the blue-green emission and shifted the emission maximum to the red region. The emission maximum returned to the blue-green region after the eld had been turned off. A model of the electric-field-induced color switching in the ZnO/polymer-based nanostructure is proposed. The bias-voltage-induced interface band bending and the deactivation of the radiative centers, in particular, singly-ionized oxygen vacancies in ZnO nanocrystals, are suggested to govern the relative changes of the blue-green-red emissions. We report on cathodoluminescence (CL) studies of the composite nanostructure obtained by spin coating of a mixture of chemically-deposited ZnO/MgO nanocrystals and a solution processable polymer (PDPV) on a Si substrate with patterned gold electrodes. The effect of an electric field on the CL of the nanostructure was studied at various bias voltages on the electrodes. A positive voltage suppressed the blue-green emission and shifted the emission maximum to the red region. The emission maximum returned to the blue-green region after the eld had been turned off. A model of the electric-field-induced color switching in the ZnO/polymer-based nanostructure is proposed. The bias-voltage-induced interface band bending and the deactivation of the radiative centers, in particular, singly-ionized oxygen vacancies in ZnO nanocrystals, are suggested to govern the relative changes of the blue-green-red emissions.
Luminescence from ZnO/MgO nanoparticle structures prepared by solution techniques
G.N.Panin,A.N.Baranov,오영제,강태원 한국물리학회 2004 Current Applied Physics Vol.4 No.6
The optical and structural properties of mixed ZnO/MgO particles prepared by solution techniques are investigated by thecathodoluminescence and electron microscopy techniques. The samples annealed at 4001000.C show well crystalline wurtzitestructure of the ZnO (MgZnO) particles with the size in range of 10100 nm. Annealing at high temperatures (>700.C) leads to Mgdiusion in ZnO and MgxZn1. xO alloy formation. The blue shifts of the near-band-edge emission as a result of the alloy band gapwidening and quantum connement eect for the small size particles are demonstrated.
The superconducting bismuth-based mixed oxides
E.V.Antipov,N.R.Khasanova,J.S.Pshirkov,S.N.Putilin,C.Bougerol,O.I.Lebedev,G.VanTendeloo,A.N.Baranov,Y.W.Park 한국물리학회 2002 Current Applied Physics Vol.2 No.5
The present paper describes the synthesis, characterization of mixed-valence bismuthates with three- or two-dimensional per-ovskite-like structures and structural criteria that inuence superconductivity in these compounds.Single-phase samples of Sr1. xKxBiO3 were prepared for the broad range of K-content: 0:256 x6 0:65. For these bismuthates thesymmetry of the structure changes from monoclinic to orthorhombic and nally to tetragonal upon increasing the K-content thusTc ¼ 12K exists in the narrow range (x . 0:50.6) within the stability eld of the tetragonal phase (0:336 x6 0:65), when the three-dimensional octahedral framework has close to the ideal perovskite structure arrangement.The layered type (Ba,K)3Bi2O7 and (Ba,K)2BiO4 bismuthates belonging to the Anþ 1BnO3nþ 1 homologous series were investi-gated. Buckling of the (BiO2 n ¼ 2 member occurs due to the ordering of alkaline- and alkaline-earthcations between two independent positions. The formation of the one-layer bismuthate was revealed by Electron Microscopy andXRPD studies. Both types of compounds are considered to be possible candidates for new superconducting materials amongbismuthates.. 2002 Published by Elsevier Science B.V.
Synthesis and Properties of Graphene Oxide/Graphene Nanostructures
O. O. Kapitanova,파닌,A. N. Baranov,강태원 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.10
We report preparation of graphene oxide (GO)/graphene (G) nanostructures and their structural, optical and electrical properties. GO was synthesized through oxidation of graphite by using the modified Hummer’s method, in which a long oxidation time was combined with a highly effective method for purifying the reaction products. The obtained GO was partially reduced (r-GO) by adding ascorbic acid and thermal annealing. An electrical reduction/oxidation process in r-GO under an electric field was used to form and control the GO/G nanostructures and the potential barrier at the interface. After the treatment, the ratio of the intensity of peak G (1578 cm−1) to that of peak D (1357 cm−1) in Raman spectra of the samples is increased, which is attributed to an increase in the ratio between the sp2 and sp3 regions. The electrical and the luminescence characteristics of the GO/G nanostructures were investigated.
Resistive Switching in Graphene/Graphene Oxide/ZnO Heterostructures
O. O. Kapitanova,파닌,O. V. Kononenko,A. N. Baranov,강태원 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.10
Planar and vertical heterostructures based on graphene/graphene oxide/ZnO nanorods were investigatedusing optical and electrical characterizations. ZnO nanorods grown on graphene substrateby using the hydrothermal method were used for local oxidation of graphene and the formation ofself-assembled graphene/graphene oxide lateral and vertical heterostructures under an electric field. The graphene substrates were prepared by deposition of graphene oxide suspensions, followed bythermal reduction or the growth of graphene by using chemical vapor deposition. The verticalheterostructure demonstrated well-reproducible resistive switching for low offset voltage and couldbe used to fabricate high-density memory devices with low power consumption.
Resistive switching in graphene/graphene oxide/ZnO heterostructures
Kapitanova, O. O.,Panin, G. N.,Kononenko, O. V.,Baranov, A. N.,Kang, T. W. 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol. No.
Planar and vertical heterostructures based on graphene/graphene oxide/ZnO nanorods were investigated using optical and electrical characterizations. ZnO nanorods grown on graphene substrate by using the hydrothermal method were used for local oxidation of graphene and the formation of self-assembled graphene/graphene oxide lateral and vertical heterostructures under an electric field. The graphene substrates were prepared by deposition of graphene oxide suspensions, followed by thermal reduction or the growth of graphene by using chemical vapor deposition. The vertical heterostructure demonstrated well-reproducible resistive switching for low offset voltage and could be used to fabricate high-density memory devices with low power consumption.