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Dive into the research topics where Konstantin I. Pokhodnya is active.

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Featured researches published by Konstantin I. Pokhodnya.


Advanced Materials | 2002

Spin‐Driven Resistance in Organic‐Based Magnetic Semiconductor V[TCNE]x

V.N. Prigodin; Nandyala P. Raju; Konstantin I. Pokhodnya; Joel S. Miller; Arthur J. Epstein

summary, we have successfully produced highly ordered arrays of single-crystalline antimony nanowires with diameters of 40 nm in porous anodic alumina membranes by pulsed electrodeposition. The results of XRD and HRTEM indicate that the nanowires have a uniform hexagonal antimony single-crystalline structure and grow along the [112 Å 0] direction. The resistance at zero magnetic field demonstrates that single-crystalline antimony nanowires with diameters of 40 nm remain metallic in character. It would be very interesting to produce a metal±semiconductor nanowire heterogeneous junction array consisting of antimony metal and bismuth semiconductor. Further work is under way. Experimental The AAM was prepared as follows: high purity (99.999 %) aluminum was electropolished at 23 V in a mixture solution of 70 % perchloric acid and etha-nol (1:9) at 4 C for 2 min. Anodization was carried out at 40 V DC in 0.25 M aqueous oxalic acid electrolyte at 7 C. After the anodization, the central sub-strate was removed in a saturated SnCl 4 solution, and the surrounding aluminum was retained as a support. Then the barrier was dissolved in 6 wt.-% phos-phoric acid solution at 30 C for 60 min. Finally, a layer of Au was sputtered onto one side of the AAM to serve as the working electrode. Field-emission microscopy observations indicate that the AAM is an almost perfect hexagonally arranged nanochannel array with a channel diameter of ~ 40 nm. The antimony plating solution consisted of 0.02 The antimony nanowire arrays were observed using a field emission microscope (JEOL JSM-6700F) and a transmission electron microscope (JEOL 200CX and JEL 2010). For TEM analysis, the specimens were prepared by dissolving the AAMs with 5 wt.-% NaOH solution, dispersing the antimony nano-wires in ethanol by ultrasonic vibration, and then placing drops of the dispersion on carbon films on a copper grid. The FEM specimen was obtained by dissolving the upper part of the AAM with 5 wt.-% NaOH solution. The X-ray diffraction spectrum was obtained using a rotating anode X-ray diffractometer (D/MAX-rA) with Cu Ka radiation (k = 1.542 x8a). The electrical resistance was measured by the standard DC four-probe method in the temperature range from 20 K to 273 K. In the past decade there has been extensive progress in using the spin property of electrons in inorganic multilayers as a means of introducing revolutionary new types of electronics (e.g., spin valves, spin light-emitting diodes) termed spin-tronics. [1] Challenges including improved …


Advanced Materials | 2010

MnII(TCNE)3/2(I3)1/2-A 3D network-structured organic-based magnet and comparison to a 2D analog

Kevin H. Stone; Peter W. Stephens; Amber C. McConnell; Endrit Shurdha; Konstantin I. Pokhodnya; Joel S. Miller

Mn{sup II}(TCNE){sub 3/2}(I{sub 3}){sub 1/2} and Mn{sup II}(TCNE)[C{sub 4}(CN){sub 8}]{sub 1/2} [tetracyanoethylene (TCNE)] are organic-based magnets with 3D and 2D extended network structures with vastly different magnetic behavior. They have similar ferrimagnetic coupled layers of Mn{sup II}(TCNE){sup {lg_bullet}-} with different interlayer couplings, which lead, respectively, to net ferrimagnetic (T{sub c} = 171 K) and antiferromagnetic (T{sub c} = 68 K) order.


Journal of Applied Physics | 2003

Anomalous magnetoresistance in high-temperature organic-based magnetic semiconducting V(TCNE)x films

N. P. Raju; T. Savrin; V.N. Prigodin; Konstantin I. Pokhodnya; Joel S. Miller; Arthur J. Epstein

Anomalous positive magnetoresistance (MR) in high temperature organic-based magnet V(TCNE)x (TCNE=tetracynoethylene) thin films is reported. MR increases linearly with applied magnetic field and shows a maximum at the ferrimagnetic ordering temperature. The suggested roles of oppositely spin polarized π* electronic subbands and magnetization fluctuations due to the disordered nature of V(TCNE)x films are discussed.


Inorganic Chemistry | 2008

Synthesis and Magnetic Properties of a [NiII(TCNE)(NCMe)2-δ][BF4] Magnet (Tc = 40 K)

Konstantin I. Pokhodnya; Victor Dokukin; Joel S. Miller

The reaction of (NBu4)(TCNE) (TCNE = tetracyanoethylene) and [Ni(NCMe)6][BF4]2 in CH2Cl2 forms layered [Ni(TCNE)(MeCN)2-delta][BF4], a magnet ( Tc = 40 K) with a ferromagnetic interaction within Ni-mu 4-[TCNE](*-) layers, and a new general route to the preparation of [M(TCNE)(NCMe)2][anion] magnets has been identified.


Journal of Physics: Condensed Matter | 2013

Carrier transport in the V[TCNE]x (TCNE = tetracyanoethylene; x ∼ 2) organic-based magnet

Konstantin I. Pokhodnya; Michael Bonner; V.N. Prigodin; Arthur J. Epstein; Joel S. Miller

The carrier transport of chemical vapor deposition (CVD) prepared films of the room temperature organic-based magnet V[TCNE]x (TCNE = tetracyanoethylene; x ~ 2) over a broad temperature and magnetic field range is reported. Due to disorder the [TCNE](·-) sites are located in statistically different environments, and their energies vary from site-to-site, which leads to tailing the density of states into the energy gap, creating electronic traps and suppressing the electron mobility. Conversely, these variations have little effect on the valence band derived from the octahedral V(II)3d(t(2g)) levels, and, hence, on the hole mobility. Presuming a Gaussian distribution of the energies of the localized states in the gap, a model that adequately describes the experimental data is proposed. In this model the T(-1) temperature dependent term was added to the Arrhenius activation energy, Ea, which effectively describes its decrease on cooling. The linear increase of positive magnetoresistance with magnetic field, as well as its weak temperature dependence [ is proportional to (1-T/Tc)(-1/2)] is discussed in terms of a small contribution to Ea associated with the change of magnetic energy.


Metamaterials | 2006

Multiple Photonic Responses in Organic Magnetic Semiconductor V(TCNE)x(x ~ 2)

Arthur J. Epstein; Jung-Woo Yoo; R. Shima Edelstein; D. M. Lincoln; N. P. Raju; Konstantin I. Pokhodnya; Joel S. Miller

A multiphotonic response in organic magnetic semiconductor V(TCNE)x (x ~ 2) with a substantial increase of conductivity induced by light (lambda=457.9 nm) is reported. Substantial decrease in activation energy for electronic hopping is due to temperature dependence of resistivity. Photoinduced effects that originated from structural changes triggered by pirarrpi* excitation in (TCNE)ldr- molecules, which leads to modulation of the magnetic exchange energy J and the activation energy DeltaE, is proposed. This mechanism for multiphotonic responses is supported by photoinduced IR studies.


Advanced Materials | 2003

Control of Coercivity in Organic-Based Solid Solution VxCo1–x[TCNE]2·zCH2Cl2 Room Temperature Magnets†

Konstantin I. Pokhodnya; Vladimir Burtman; Arthur J. Epstein; James W. Raebiger; Joel S. Miller


Chemistry of Materials | 2004

Solid Solution VxFe1-x[TCNE]2·zCH2Cl2 Room-Temperature Magnets

Konstantin I. Pokhodnya; Elaine B. Vickers; Michael Bonner; and Arthur J. Epstein; Joel S. Miller


Chemistry of Materials | 2004

Parylene protection coatings for thin film V[TCNE]x room temperature magnets

Konstantin I. Pokhodnya; Michael Bonner; Joel S. Miller


Physical Review B | 2009

Direct evidence of electron spin polarization from an organic-based magnet: [FeII(TCNE)(NCMe)2][FeIIICl4]

Anthony N. Caruso; Konstantin I. Pokhodnya; William W. Shum; W. Y. Ching; Bridger Anderson; Marshall T. Bremer; E. Vescovo; Paul Rulis; Arthur J. Epstein; Joel S. Miller

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Kevin H. Stone

SLAC National Accelerator Laboratory

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Peter W. Stephens

State University of New York System

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