bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochar Production, Activation and Application as a Promising Catalyst
Authors: Wang Shurong , Zhu Lingjun , Ma Zhongqing
Published: July 2018

This chapter introduces the basic theory and technologies of biochar production, biochar activation and upgrading, and biochar application as a promising catalyst. The routes of biochar production including conventional pyrolysis, gasification, microwave assisted pyrolysis and hydrothermal carbonization are described in detail. The yield and properties of biochar, such as high heating value, pH value and BET surface area and pore structure, and also the graphitization degree, are significantly affected by operating conditions, temperature, heating rate, solid residence time, particle size, etc. To enhance the pore volume, control the pore diameter, and improve the surface area of primary biochar, physical activation, chemical activation, and the physicochemical activation are the main technologies. After activation, biochar has a relatively high surface area and pore volume possessing a multi-level porous structure with both micropores and mesopores. And the functional groups on the surface of biochar facilitate its surface chemistry modification. Because of all of these properties, biochar has a great potential for application as a catalyst and catalyst support. The catalyst applications summarized in this chapter include the direct application of biochar as a catalyst for biomass thermoconversion and tar removal, heterogeneous catalyst support for hydrocarbons production, solid acid catalyst for biodiesel production, electrochemical catalyst and photocatalyst.
Development of a flow injection analytical system for short chain amide determination based on a tubular bioreactor and an ammonium sensor
Authors: Veríssimo Marta I. S. , Oliveira Sara B. , Silva Nelson A. F. , Matos Manuel , Karmali Amin , Gomes M. Teresa S. R.
Published: July 2018

Flow injection bio-analyzer for fast amide determination.
Electrochemical N2fixation to NH3under ambient conditions: Mo2N nanorod as a highly efficient and selective catalyst
Authors: Ren Xiang , Cui Guanwei , Chen Liang , Xie Fengyu , Wei Qin , Tian Ziqi , Sun Xuping
Published: July 2018

Mo2N/GCE behaves as a highly efficient electrocatalyst for NRR under ambient conditions with high Faradaic efficiency (4.5%) and NH3yield (78.4 μg h−1mgcat.−1).
ESIPT-based fluorescence probe for the rapid detection of hypochlorite (HOCl/ClO−)
Authors: Wu Luling , Yang Qingye , Liu Liyuan , Sedgwick Adam C. , Cresswell Alexander J. , Bull Steven D. , Huang Chusen , James Tony D.
Published: July 2018

ESIPT-based fluorescence probes are emerging as an attractive tool for the detection of biologically relevant analytes owing to their unique photophysical properties.
(Deep) blue through-space conjugated TADF emitters based on [2.2]paracyclophanes
Authors: Spuling Eduard , Sharma Nidhi , Samuel Ifor D. W. , Zysman-Colman Eli , Bräse Stefan
Published: July 2018

The first examples of through-space conjugated thermally activated delayed fluorescence (TADF) emitters based on a [2.2]paracyclophane (PCP) skeleton with stacked (coplanar) donor–acceptor groups have been synthesized.
Performance-improved vertical GaN-based light-emitting diodes on Si substrates through designing the epitaxial structure
Authors: Wang Wenliang , Li Yuan , Zheng Yulin , Yang Zhichao , Lin Zhiting , Chen Xiaofeng , Lu Zhenya , Li Guoqiang
Published: July 2018

Performance-improved vertical GaN-based light-emitting diodes (LEDs) have been fabricated on Si substrates through designing the epitaxial structures with a combination of an AlN interlayer and a SiNxinterlayer.
Solvation of Al3+ cations in bulk and confined protic ionic liquids: a computational study
Authors: Gómez-González Víctor , Docampo-Álvarez Borja , Montes-Campos Hadrián , Otero Juan Carlos , Lago Elena López , Cabeza Oscar , Gallego Luis J. , Varela Luis M.
Published: July 2018

Nanostructured solvation of Al3+ in an EAN ionic liquid, forming octahedral complexes with nitrate anions.
Epitaxial growth and physical properties of 2D materials beyond graphene: from monatomic materials to binary compounds
Authors: Li Geng , Zhang Yu-Yang , Guo Hui , Huang Li , Lu Hongliang , Lin Xiao , Wang Ye-Liang , Du Shixuan , Gao Hong-Jun
Published: July 2018

This review highlights the recent advances of epitaxial growth of 2D materials beyond graphene.
Oxide/sulfide-based hybrid arrays as robust electrocatalysts for water splitting
Authors: Du Xiaoqiang , Wang Qibin , Li Yu , Zhang Xiaoshuang
Published: July 2018

NiCo2O4/Ni3S2 affords a current density of 10 mA cm−2 in 1.0 M KOH at a cell voltage of 1.58 V, i.e., comparable to that of the commercial 20 wt% IrO2/C–40 wt% Pt/C couple (1.52 V at 10 mA cm−2).
Up-conversion luminescence, thermometry, and optical heating properties of Er3+- and Yb3+-doped K2LaNb5O15submicro-particles synthesized by a simple molten salt method
Authors: Li Mengzhu , Shi Yong , Zhao Chuanzhen , Yang Fengming , Li Qiuyue , Zhang Xinxing , Wu Shengcheng , Chen Haiyan , Liu Junming , Wei Tong
Published: July 2018

Variation of the calculated slope valuesversus Ts(a) andSplots of KLN:0.04Er3+/Yb3+prepared at differentTsvalues (b).
Silk fibroin nanoparticles as biocompatible nanocarriers of a novel light-responsive CO-prodrug
Authors: Jiménez-Amezcua Ignacio , Carmona Francisco J. , Romero-García Ignacio , Quirós Miguel , Cenis José L. , Lozano-Pérez A. Abel , Maldonado Carmen R. , Barea Elisa
Published: July 2018

Silk fibroin nanoparticles have been used as platforms of a new photoactive CO-prodrug leading to a hybrid material with enhanced CO-release.
Constructing reactive Fe and Co complexes from isolated picolyl-functionalized N-heterocyclic carbenes
Authors: Liang Qiuming , Liu Nina Jiabao , Song Datong
Published: July 2018

The Fe(ii) and Co(ii) complexes prepared from the isolated free carbene form of the picolyl-NHC ligands display excellent catalytic activity towards the hydrosilylation of ketones.
Hydrazone-based hole transporting material prepared via condensation chemistry as alternative for cross-coupling chemistry for perovskite solar cells
Authors: Petrus Michiel L. , Sirtl Maximilian T. , Closs Anna C. , Bein Thomas , Docampo Pablo
Published: July 2018

We introduce a new class of HTMs that are based on a hydrazone-backbone to the field of perovskite solar cells. The simple synthesis allows these materials to be produced at a low-cost.
Crystallisation of organic molecules with a remarkably suppressed coffee-ring effect by a drop-drying process using binary solvent core–shell droplets
Authors: Ahn Yoolim , Park Yohwan , Koo Jin Young , Choi Hee Cheul
Published: July 2018

A modified drop-drying method was developed using a core–shell droplet which is spontaneously formed from a methanol/mesitylene binary solvent system.
DN strategy constructed photo-crosslinked PVA/CNC/P(NIPPAm-co-AA) hydrogels with temperature-sensitive and pH-sensitive properties
Authors: Li Zhangkang , Bai Huiyu , Zhang Shengwen , Wang Wei , Ma Piming , Dong Weifu
Published: July 2018

The surface and cross-section morphologies of PVA/CNC/P(NIPPAm-co-AA) hydrogels exhibited double-network (DN) and uniform network structures due to the introduction of PNIPAAm and PAA through the photo-crosslinking technology.
Long-term stability of dye-sensitized solar cells using a facile gel polymer electrolyte
Authors: Ma’alinia A. , Asgari Moghaddam H. , Nouri E. , Mohammadi M. R.
Published: July 2018

Hydroxypropyl cellulose as a polymeric gelator agent was incorporated in the liquid electrolyte of dye-sensitized solar cells, showing long-term stability and efficient performance.
Imaging of lysosomal pH changes with a novel quinoline/benzothiazole probe
Authors: Fan Li , Nan Ming , Ge Jinyin , Wang Xiaodong , Lin Bo , Zhang Wenjia , Shuang Shaomin , Dong Chuan
Published: July 2018

A fluorescent pH probeBTVQfor imaging lysosomal pH fluctuations in live cells and extreme acidity inE. colicells.
Theoretical insight into the mechanism, regioselectivity, and substituent group effect of Rh-catalyzed synthesis of 1,2-benzothiazines from NH-sulfoximines and diazo compounds
Authors: Yan Jing , Liu Chengbu , Zhang Dongju
Published: July 2018

A theoretical study of Rh-catalyzed synthesis of 1,2-benzothiazines from NH-sulfoximines and diazo compounds.
Sterically shielded tetrazoles for a fluorogenic photoclick reaction: tuning cycloaddition rate and product fluorescence
Authors: An Peng , Lin Qing
Published: July 2018

We report the reactivity and fluorescence studies of a panel of sterically shielded tetrazoles with different N-aryl groups in the fluorogenic photoclick reaction with spiro[2.3]hex-1-ene.
A CEMP-no star in the ultra-faint dwarf galaxy Pisces II
Authors: Spite M. , Spite F. , François P. , Bonifacio P. , Caffau E. , Salvadori S.
Published: July 2018

Aims. A probable carbon enhanced metal-poor (CEMP) star, Pisces II 10694, was discovered recently in the ultra-faint (UFD) galaxy Pisces II. This galaxy is supposed to be very old, suspected to include dark matter, and likely formed the bulk of its stars before the reionisation of the Universe.

Methods. New abundances have been obtained from observations of Pisces II 10694 at the Kueyen ESO VLT telescope, using the high-efficiency spectrograph: X-shooter.

Results. We found that Pisces II 10694 is a CEMP-no star with [Fe/H] = −2.60 dex. Careful measurements of the CH and C2  bands confirm the enhancement of the C abundance ([C/Fe] = +1.23). This cool giant has very probably undergone extra mixing and thus its original C abundance could be even higher. Nitrogen, O, Na, and Mg are also strongly enhanced, but from Ca to Ni the ratios [X/Fe] are similar to those observed in classical very metal-poor stars. With its low Ba abundance ([Ba/Fe] = −1.10 dex) Pisces II 10694 is a CEMP-no star. No variation in the radial velocity could be detected between 2015 and 2017. The pattern of the elements has a shape similar to the pattern found in galactic CEMP-no stars like CS 22949-037 ([Fe/H] = −4.0) or SDSS J1349+1407 ([Fe/H] = −3.6).

Conclusions. The existence of a CEMP-no star in the UFD galaxy Pisc II suggests that this small galaxy likely hosted zero-metallicity stars. This is consistent with theoretical predictions of cosmological models supporting the idea that UFD galaxies are the living fossils of the first star-forming systems.
Effects of average grain size on the magnetic properties of permalloy films
Authors: Djuzhev Nikolay , Iurov Aleksey , Mazurkin Nikita , Chinenkov Maksim , Trifonov Aleksey , Pushkina Marina
Published: July 2018

In this paper the results of substrate temperature effects on average grain size in FeNi 20:80 are shown. It was found that with an increase of the substrate temperature from 270 to 390 °C, the anisotropic magnetoresistive (AMR) effect increases from 1.2 to 2.3% and the coercive force from 1.6 to 5.3 Oe. The presence of two conflicting processes: the task of increasing AMR effect to achieve high sensitivity of AMR-sensor and to decrease the coercive force to increase the precision of conversion, leads to the necessity to find the optimum deposition temperature of the permalloy film. The dependence of the AMR effect and the coercive force on the substrate temperature during deposition was obtained. This dependence shows that the substrate temperature increasing above 320 °C leads to coercive force increasing and does not lead to a substantial AMR increasing. In this regard, the substrate temperature 320 °C was determined as optimal.
Top and Bottom Spin Valves With Ni-Fe-Mn Antiferromagnetic Layer
Authors: Blinov Ilya , Krinitsina Tatiana , Milyaev Mikhail , Popov Vladimir , Ustinov Vladimir
Published: July 2018

Structure, magnetic and magnetoresistive properties of spin valves with Ni-Fe-Mn antiferromagnet as a pinning layer have been studied. A technique of fabrication of spin valves with an enhanced thermal stability and improved hysteretic characteristics has been elaborated.
Critical switching characteristics of three-layered spin valve for different materials and alloys with uniaxial anisotropy
Authors: Iusipova Iuliia
Published: July 2018

We analyze the dependence of the current density and magnetic field switching on the magnetic parameters of the material of the ferromagnetic layers of the spin valve. Comparison of critical characteristics of the spin valve with longitudinal anisotropy of ferromagnetic layers fabricared of different materials showed that the promising materials for the fabrication of spin valve are cobalt, iron, their alloys, ferroborates of cobalt and alloys of cobalt with gadolinium. For these materials we produced and analyzed the bifurcation diagrams of equations describing the switching process of the spin valve. Based on the study of the dynamics of the magnetization vector we obtained the numerical evaluation of time switching.
Tunnel Magnetoresistive Effect in Nanostructured Composite Systems
Authors: Stognei O.V. , Sitnikov A.V. , Kalinin Yu.E.
Published: July 2018

The results of the investigation of tunnel magnetoresistive effect in a large number of metal-dielectric nanocomposites obtained by the same technology and under identical conditions are presented. The composites with multi-elemental amorphous metal phase were considered. It has been shown that the large values of the tunnel magnetoresistive effect in these composites are ensured when the value of the density of electronic states on the Fermi surface is large while other conditions are being equal. The conditions for the appearance of an anomalous positive tunneling magnetoresistance are formulated based on the study of composites with a mono-elemental ferromagnetic phase from cobalt.
Investigation of InSb:Mn thin films magnetoresistance by I-V characteristics method
Authors: Novodvorsky Oleg , Mikhalevsky Vladimir , Parshina Liubov , Khramova Olga , Lotin Andrey , Cherebylo Elena , Marenkin Sergey , Aronov Aleksey , Kochura Aleksey , Panchenko Vladislav
Published: July 2018

We have investigated the effect of magnetoresistance in the thin films of InSb:Mn using the data of I-V curves. The thin films were produced by pulsed laser deposition (PLD) method from the InSb+MnSb composite alloy targets with the concentrations of MnSb to 20%. The temperature dependence of magnetoresistance of the films has been studied in the temperature range from 10K to 300K.
Numerical simulation of spin transport in systems with complex geometry
Authors: Andrianov Timofey , Vedyayev Anatoly
Published: July 2018

The spin diffusion and charge equations in Levy-Fert and Waintal models were numerically solved, using finite element method in complex non-collinear geometry with strongly inhomogeneous current flow. As an illustration, spin-dependent transport through a magnetic pillar and nonmagnetic spacer separating two magnetic layers was investigated. It is shown, that the structure with number of pillars gives a higher value of Giant Magnetoresistance (GMR) effect rather than a structure with one pillar of equivalent diameter. The inhomogeneity of spin currents, which has one of the strongest impacts on GMR effect value leads to the occurrence of spin-current vortices. Introduction of lT and lL lengths in Waintal model gives a better description of angular dependence of GMR effect rather than Levy-Fert model.
THE INFLUENCE OF “INJECTED” AND “THERMAL” MAGNONS ON A SPIN WAVE CURRENT AND DRAG EFFECT IN HYBRID STRUCTURES
Authors: Lyapilin Igor , Okorokov Mikhail
Published: July 2018

The formation of the two: injected and thermally excited, different in energies magnon subsystems and the influence of its interaction with phonons and between on drag effect under spin Seebeck effect conditions in the magnetic insulator part of the metal/ferromagnetic insulator/metal structure is studied. The analysis of the macroscopic momentum balance equations of the systems of interest conducted for different ratios of the drift velocities of the magnon and phonon currents show that the injected magnons relaxation on the thermal ones is possible to be dominant over its relaxation on phonons. This interaction will be the defining in the forming of the temperature dependence of the spin-wave current under spin Seebeck effect conditions, and inelastic part of the magnon-magnon interaction is the dominant spin relaxation mechanism.
INVESTIGATION OF ANGULAR AND TEMPERATURE DEPENDENCE OF SPIN-WAVE RESONANCE SPECTRA IN MULTILAYER MAGNETIC FILMS
Authors: Bazhanov Andrey
Published: July 2018

In this letter we study the dependences of the resonance field Hn and the linewidth 2ΔHn of the spin-wave resonance (SWR) modes in two-layer ferrite-garnet films with dissipative and mixed spinpinning mechanisms. It is established that for films with a dissipative mechanism of spin pinning, the increase in the linewidth at ΘH = 35° is associated with the maximum misorientation between the external magnetic field and the direction of the equilibrium magnetization of the sample. For films with a mixed spin-pinning mechanism, an increase in the linewidth 2ΔHn with increasing angle ΘH is associated with an increase in the depth of penetration of the spin wave into the pinning layer for such films. On the temperature dependence of the linewidth 2ΔHn for samples with a mixed fixation mechanism at a perpendicular orientation, an increase in the width of the absorption peak lines is observed. And with an increase in the peak number, the maximum of the linewidth shifts to the low-temperature region. With parallel orientation, the linewidth 2ΔHn in a wide temperature range from 20°C to 200°C remains practically unchanged.
Experimental study of microwave properties of composites filled with Permalloy powder
Authors: Bobrovskii Stanislav Y. , Garanov Victor A. , Naboko Andrei S. , Osipov Alexei V. , Rozanov Konstantin N.
Published: July 2018

Frequency dependencies of permittivity and permeability of composites filled with Permalloy powder with various concentrations and shapes of particles have been measured and discussed. The powder particles of various shapes were obtained by mechanical milling of industrial Permalloy powder in organic media. Paraffin wax was used as a matrix for producing the composites. A shape data of the particles was obtained with an electron microscope. The permittivity and permeability were measured in the frequency range of 0.13 to 10 GHz. The shape of the particles changes from sphere to platelet with increase of milling time. The change leads to a shift of the ferromagnetic resonance (FMR) frequency and magnetic loss peak. It is shown that for larger particles, a decrease of the Q-factor of the ferromagnetic resonance is observed, which is explained by the strong influence of the skin effect. With increase of the concentration of the Permalloy particles in composite, the magnetic loss peak shifts to low frequencies. When the spherical particles are flattened, the resonance frequency shifts to high frequencies, which indicates that the shift to high frequencies due to the decrease of the skin effect and the change in the magnetic structure is stronger than the shift to the low frequencies by changing the shape and reducing the demagnetization.
Conditions for division and multiplication of frequencies in ferrite
Authors: Pleshev Dmitriy , Vlasov Vladimir , Asadullin Fanur , Kotov Leonid , Poleshchikov Sergey , Shavrov Vladimir , Shcheglov Vladimir
Published: July 2018

The paper considers investigation of hypersound magnetic and elastic oscillations excitation by use of alternating magnetic field in normal magnetized plate. Distinctive features of frequency division and multiplication are studied in the paper. The relation between processes of frequency division and multiplication and structure of the plate as well as parameters of saturation magnetization, anisotropy constant, magnetic and elastic damping has been revealed.
Superdirected beam of the backward volume spin wave
Authors: Annenkov Alexander Yu. , Gerus Sergey V. , Lock Edwin H.
Published: July 2018

Visualized patterns of the backward volume spin wave (BVSW) excited by arbitrarily oriented linear transducer in tangentially magnetized ferrite film are investigated experimentally in the plane of ferrite film for the case where the transducer length D is much larger than the wavelength λ0. Superdirected BVSW beam having zero angular width and minimal smearing of the beam energy along the film surface is observed experimentally. Thus, it is proved that such phenomenon as “superdirected propagation of the wave” exists in the nature.
Study of torque acting on magnetization during 180° pulsed reversal process in ferrite-garnet films with biaxial anisotropy
Authors: Kolotov Oleg , Matyunin Andrey , Nikoladze Georgiy , Polyakov Petr
Published: July 2018

The mode of 180° a pulsed magnetization reversal process of ferrite-garnet films with in-plane anisotropy in the external fields region, in which the mechanism of the homogeneous rotation of magnetization takes place, was firstly investigated. Analysis of calculated and experimental longitudinal signals showed that the presence of biaxial anisotropy in real ferrite-garnet film leads to the occurrence of nonlinear damped magnetization oscillations (with a period of the main harmonic of ~1.5 ns).
Measurement of magnetic noise in magnetoimpedance sensing element
Authors: Antonov Anatoliy S. , Buznikov Nikita A. , Sultan-Zade Timur T. , Shkliaev Alexey A.
Published: July 2018

A method for measurement of magnetic noise in magnetoimpedance sensing element is proposed. Glass-coated Co-based amorphous microwires with a slightly negative magnetostriction were used as the sensing element. The operation principle of the sensing element was based on the nonlinear off-diagonal magnetoimpedance, when field dependent higher harmonic components appeared in voltage in the pick-up coil wound around the microwire. The magnetic noise for the second harmonic in the pick-up coil voltage was studied. The dependences of the magnetic noise and the signal-to-noise ratio in the sensitive element on the current amplitude were analyzed. The noise performance of the second harmonic in the pick-up coil voltage was compared to that for a flux-gate sensing element.
Dispersion of the magnetostatic volume waves in a medium with damping
Authors: Maltceva Lidiya , Makarov Pavel , Kotov Leonid , Shcheglov Vladimir
Published: July 2018

In magnetostatic approximation of electrodynamics the dispersion relation for magnetostatic back-ward volume waves (MSBVW) in a ferrite film, placed in a constant longitudinal and transverse alternating magnetic field is obtained. The magnetic field, damping and temperature influence on the spectrum and dispersion characteristics of the MSBVW is regarded.
Rotational remagnetization and orientational transitions in submicron YIG films
Authors: Vladyslav Poimanov , Yurii Nepochatykh , Victor Koledov , Vladimir Shavrov
Published: July 2018

It is shown that for the quasinormal remagnetization of the submicron YIG films with the normal along the [111] axis, which are in the single-domain state, two types of orientation transitions (OT) due to the influence of easy axes can be distinguished. The nonreciprocity of the FMR spectrum for forward and reverse magnetization due to the influence of easy axes is shown.
Monte Carlo simulation of aging phenomena in multilayer magnetic structures
Authors: Purtov Alexandr N. , Mamonova Marina V. , Prudnikov Vladimir V. , Prudnikov Pavel V.
Published: July 2018

A Monte Carlo simulation of the non-equilibrium behavior of multilayer magnetic structures consisting of alternating magnetic and nonmagnetic nanolayers is realized. The calculated two-time autocorrelation function for the structure during its evolution starting from high-temperature initial state is analyzed. The analysis reveals aging effects characterized by a slowing down of correlation characteristics in the system with increase of the waiting time. The dependence of aging characteristics on thickness of ferromagnetic films is investigated. It is shown that, in contrast to bulk magnetic systems, the aging effects in magnetic superstructures arise not only at the ferromagnetic ordering temperature Tc in the films but also within a wide temperature range at T ≤ Tc.
Structural and magnetic characteristics of the Co/Cu/Co thin-film systems
Authors: Shalygina Elena , Kharlamova Anna , Makarov Andrey , Kurlyandskaya Galina , Svalov Andrey
Published: July 2018

The results on investigation of structural and magnetic characteristics of Co/Cu/Co thin-film systems obtained by magnetron sputtering on glass substrates are presented. The thickness of Co layers in all samples is equal to 5 nm and the Cu layer is varied from 0.5 to 4 nm. It is found that the saturation field, HS, oscillates in magnitude with increasing Cu layer thickness with the period of the order of 1 nm. The maximum values of HS are observed for tCu = 1.4, 2.2 and 3.2 nm. The hysteresis loops measured for these samples in a magnetic field applied along the easy magnetization axis have a two-step form, and for other tCu – rectangular one. The obtained results are explained by the presence of exchange coupling between the ferromagnetic layers through a Co spacer and its oscillating behavior with changing tCu.
Microwave and magneto-optic properties of ε-Fe2O3 nanoparticles arising in borate glasses doped with Fe and Gd
Authors: Ivanova Oxana , Kliava Janis , Edelman Irina , Ivantsov Ruslan , Petrakovskaja Eleonora
Published: July 2018

The ε-Fe2O3 nanoparticles in borate glasses co-doped with low concentrations of Fe2O3 and Gd2O3 were investigated with two experimental techniques – visible magnetic circular dichroism (MCD) and electron spin resonance (ESR). The most prominent features of the MCD spectra are: non-linear dependence of the spectral maxima intensities on the Gd concentration and strong increase with the temperature decrease. The ESR spectra of these glasses exhibit two features with g = 4.3 due to the diluted Fe3+ ions and 2.0 associated both with Fe3+ ions and with nanoparticles. The integrated spectra intensities do not follow the T-1 Curie law suggesting a considerable contribution from the magnetically ordered nanoparticles to ESR. Analysis of the MCD and ESR concentration dependences allow suggestion on the Gd ions incorporation into nanoparticles.
Effect of chemical ordering on optical properties of Fe3Si epitaxial films
Authors: Tarasov Ivan , Popov Zakhar , Visotin Maxim , Yakovlev Ivan , Varnakov Sergey
Published: July 2018

Optical characteristics (electron energy loss function, optical conductivity σ, permittivity ε, refractive index n, extinction coefficient k, and absorption coefficient α) of a 30 nm thick epitaxial Fe3Si iron silicide films grown at different silicon substrate temperature (26, 100, 200, 300 ˚C) were determined within E = 0.74–6.46 eV photon energy range using spectroscopic ellipsometry technique. The experimental data are compared to the optical characteristics calculated in the framework of the density functional theory using the GGA–PBE approximation. Variations of the optical characteristics spectra are discussed from the point of view of chemical ordering of DO3 type crystal structure. It is asserted that the electron energy-loss function, optical conductivity and extinction coefficient of the Fe3Si iron silicide films undergo noticeable changes in different spectral ranges over the whole spectrum between 0.74 and 6.46 eV due to variation in the chemical order. Information on the effect of chemical ordering on the optical properties obtained here allows one to carry out quick qualitative analysis of Fe3Si film crystal quality during the synthesis procedures by ellipsometry method in situ.
MAGNETO-OPTICAL AND MAGNETIC RESONANCE PROPERTIES OF NANO-SCALED GRANULAR FILMS (CoFeB)x(SiO2)100-x and (CoFeB)xС100-x
Authors: Vyzulin Sergey , Gan’shina Elena , Garshin Vladimir , Perova Natalia , Syr’ev Nikolaj
Published: July 2018

The results of experimental studies of magneto-optical (MO) and magnetic resonance (MR) properties of nanogranular film structures (CoFeB)x(SiO2)100-x and (CoFeB)xС100-x obtained by the ion-beam sputtering method are presented. Magnetic spectra were registered by the method of ferromagnetic resonance (FMR), and magneto-optical spectra were registered by observation of Transversal Kerr Effect (TKE). A comparative analysis of the experimental MO spectra and FMR spectra for systems (CoFeB)x(SiO2)100-x and (CoFeB)xС100-x indicates that a multi-phase structure realizes in the (CoFeB)xС100-x system. The existence of a multiphase structure is associated with possible plasma-chemical processes that can occur during the synthesis of nanosystems with carbon.
Influence of hydrogenation on magnetoresonance characteristics of nanocomposite (CoFeB)mC100-m films
Authors: Vyzulin Sergei , Kevraletin Alexandr , Syr’ev Nikolaj
Published: July 2018

The influence of hydrogenation on the magnetoresonance characteristics of nanocomposite films during synthesis is studied by the method of ferromagnetic resonance (FMR). It is shown that introduction of hydrogen into the working chamber during the synthesis of film nanogranular structures (CoFeB)mC100-m leads to a change in a resonant field, to increase of the absorption line width, to reduction of anisotropy field in the film plane.
Ferromagnetic resonance and random magnetic anisotropy in nanocrystalline Fe-Zr-N films
Authors: Sheftel Elena , Harin Eugene , Tedzhetov Valentin , Koksharov Yuri
Published: July 2018

The effective magnetic anisotropy of the ferromagnetic nanocrystalline Fe-Zr-N films prepared by magnetron sputtering under different conditions has been determined by both correlation magnetometry and ferromagnetic resonance methods. The effective magnetic anisotropy values obtained by the two methods are compared and the origin of the values is discussed.
Optical and magnetic properties of Al/NiFe and Al/Ge/NiFe nanosized films
Authors: Hashim H. , Singh S.P. , Panina L.V. , Pudonin F.A. , Sherstnev I.A. , Podgornaya S.V. , Shpetnyy I.
Published: July 2018

Nanosized films with ferromagnetic layers are widely used in nanoelectronics, sensor systems and telecommunication. The physical and magnetic properties of nanolayers may significantly differ from those known for bulk materials due to fine crystalline structure, influence of interfaces, roughness, and diffusion. In this work, we are employing a spectral ellipsometry method, magneto-optical Kerr magnetometry and VSM to investigate the impact of layer thickness on the optical constants and magnetization processes for two and three layer films of the type Al/NiFe/sitall, Al/Ge/NiFe/sitall on sitall substrate for different thickness of the upper Al layers. The refractive indexes of two layer films are well resolved by spectral ellipsometry demonstrating their good quality. Modelling data for three-layer films show considerable discrepancy with the experiment, which can be related to a stronger influence of interfaces. The magnetization processes of two-layer films weakly depend on the type and thickness of the upper non-ferromagnetic layers. However, the coercivity of three layer films may significantly change with the thickness of the upper layer: more than twice when the thickness of Al layer increases from 4 to 20 nm.
Monte Carlo study of magnetic structures in rare-earth amorphous alloys
Authors: Bondarev Alexey , Bataronov Igor
Published: July 2018

Using the Monte Carlo method, we studied magnetic properties of the models of Re-Tb and Re-Gd amorphous alloys as well as pure amorphous Tb and Gd. The magnetic phase diagrams for the models of amorphous Tb and Gd were constructed. We determined the values of D/J0 (for Tb) and J1/|J2| (for Gd) at which the transition into spin-glass-like state takes place. The local magnetic structure was studied by the spin correlation functions and the angular spin correlation functions. The difference in magnetic structures in amorphous alloys with the random anisotropy and with fluctuations of exchange interaction was revealed.
Magnetic investigation of low temperature phase transition in iron selenides
Authors: Tigran Baluyan , Alla Novakova , Marat Khairullin
Published: July 2018

3c-and 4c-Fe7Se8 contain large amount of ordered vacancies that define its magnetic structure. Combined comparative magnetic and Mossbauer investigation were performed to find out the peculiarities of the temperature magnetic transitions in these compounds. It was found that adding an additional layer with ordered vacancies in 4c superstructure increased the temperature of spin rotation.
Magnetic properties of the non-stoichiometric TbCo2Nix alloys
Authors: Inishev Alexander , Gerasimov Evgeny , Mushnikov Nikolay , Terentev Pavel , Gaviko Vasily
Published: July 2018

The magnetic and magnetothermal properties of the non-stoichiometric TbCo2Nix (0 ≤ x ≤ 0.2) alloys were studied. It was found that the concentration dependence of the Curie temperature and magnetic moment of the 3d-sublattice have a maximum at x = 0.025. The obtained experimental magnetic properties of the TbCo2Nix alloys were discussed under assumption that the Co magnetic moment in the compounds changes with increasing x. The magnetic entropy change was determined using the temperature dependences of the magnetization and Maxwell’s thermodynamic relation. The obtained results for TbCo2Nix were compared with those for the ErCo2Mnx alloys.
Structural and magnetic anisotropy of directionally-crystallized ferromagnetic microwires
Authors: Evstigneeva Svetlana , Morchenko Alexander , Trukhanov Alexey , Panina Larissa , Larin Vladimir , Volodina Natalia , Yudanov Nikolay , Nematov Makhsudsho , Hashim Hisham , Ahmad Haseeb
Published: July 2018

Amorphous ferromagnetic microwires have drawn attention primarily due to their excellent soft magnetic properties as the elements of sensors. In this work, semi-hard magnetic microwires of composition Fe4.3Co67.7Si11B14Cr3 were obtained after a process of directional crystallization from amorphous state. The XRD analysis of crushed and whole wires identified the formation of the face-centered Co-modification as the main phase of directionally crystallized core alloy, which explains a large increase in anisotropy and coercivity. The application of a magnetic field during crystallization may orient the easy anisotropy axis of crystallites along the wire. This is confirmed by the investigation of crystallite orientation with respect to the wire axis and X-rays direction in diffractometer. The obtained results revealed that the formation of crystallites in amorphous Co-rich microwires occurs with the predominant orientation of the crystallographic direction [111] along the wire axis and the direction of a magnetic field during the directional crystallization process.
Static and high-frequency magnetic properties of nanocrystalline Fe-Zr-N films
Authors: Sheftel Elena , Harin Eugene , Tedzhetov Valentin , Rozanov Konstantin , Zezyulina Polina , Bobrovskii Stanislav , Kiryukhantsev-Korneev Philipp
Published: July 2018

The phase and structural states of nanocrystalline Fe-based films alloyed with Zr and N, which were prepared by reactive magnetron sputtering under different conditions, magnetic-structure parameters of the films and their static and high-frequency magnetic properties have been studied. The interrelation of static magnetic properties and magnetic-structure parameters with the value of real effective magnetic permeability μ’ and frequency range, for which the value is unchanged, has been studied.
Spontaneous magnetization reversal caused by magnetic noise in ε-In0.24Fe1.76O3 nanoparticles
Authors: Dmitriev Alexei
Published: July 2018

Kinetics of magnetization relaxation of the exotic ε-In0.24Fe1.76O3 nanoparticles under applied magnetic field has been studied. The fluctuation field and the activation volume have been calculated from the magnetic viscosity data. The relation between magnetic viscosity and magnetic noise caused by the random thermally activated magnetization reversal of a single nanoparticle has been established. Stepped sweeping of magnetic field expands the windows of experimentally detectable magnetic fluctuations. The changes in the reversal magnetic field provide ε-In0.24Fe1.76O3 nanoparticles scanning and sorting them by magnetic noise frequency.
Visualization of magnetostructural transition in Heusler alloys by Magnetic Force Microscopy
Authors: Geydt Pavel , Rodionov Igor D. , Granovsky Alexander B. , Soboleva Ekaterina , Fadeev Egor , Titov Ivan S. , Dubenko Igor , Lähderanta Erkki
Published: July 2018

Magnetostructural transition was observed in Ni-Mn-In-Cr Heusler alloy with help of Magnetic Force Microscopy (MFM). The crystal structure of a sample and characteristic temperatures of the phase transition were controlled by roentgenostructural phase analysis and magnetometry, respectively. It appeared prominently important to prepare the surface of the sample until the nanometer level of surface roughness. Magnetic study performed with scanning probe microscope revealed existence of magnetic domains, which were spread across the surface evenly. Further studies revealed that intensity of magnetic signal decreases as fading out of the contrast of the MFM images. It was found that location of domains shifted after the heating/cooling cycle above Curie temperature for the studied alloy. Location of new domain walls appeared correlating with surface scrapings and defects, whilst it became independent from those after heating until just 70°C. The mechanism behind the observed transition is proposed.
Investigation of structural and magnetic properties of Fe-Rh-(Z) (Z = Co, Pt) alloys by first principles method
Authors: Pavlukhina Oksana , Sokolovskiy Vladimir , Zagrebin Mikhail , Buchelnikov Vasily
Published: July 2018

In this work, we present theoretical investigations of the structural and magnetic properties Fe (Rh, Co) and Fe (Rh, Pt) alloys using the density functional theory. The energy calculations were performed for the 16-atom supercell (Fe8Rh8-xZx) with different initial spin configurations. It is shown that a small variation of Pt or Co content leads to change the type of magnetic ordering. It is shown that the ferromagnetic configuration of Fe8Rh8-xCox (x=2, 3) is more energetically favorable as compared with other configurations in austenite. The antiferromagnetic configuration is more energetically favorable for Fe8Rh7Co1 alloy. For the Fe8Rh8-xPtx system, the checkerboard-like antiferromagnetic configuration was found to be more energetically favorable. Besides, the addition of Pt into Fe-Rh system slightly changes the optimized lattice parameter and stimulates the martensitic phase transformation.
Giant magnetocaloric effect in composites based on polymeric matrix and manganese arsenide
Authors: Pankratov Nikolay , Mitsiuk Victor , Vetcher Alexander , Krokhotin Andrei , Govor Gennadiy , Nikitin Sergey
Published: July 2018

A field and/or temperature hysteresis is more than just an interesting incomprehensibility that occurs in materials with a first-order magnetic transition. Indeed, the reversibility of the magnetocaloric effect (MCE), being essential for magnetic heat pumps, strongly depends on the width of the thermal hysteresis and, therefore, it is necessary to find solutions to minimize losses associated with thermal hysteresis in order to maximize the efficiency of magnetic cooling devices. In this work, the polymer matrix composites with MnAs powder as reinforcing material were obtained and its MCE by direct method was studied. The influence of composite preparation process on the MCE was investigated. It was found that the MCE of bulk MnAs shows strong temperature hysteresis caused by magnetostructural transition from paramagnetic to ferromagnetic state, which also leads to an irreversible MCE at cooling at first magnetization. The reversible MCE of bulk MnAs in field 12.5 kOe is ΔT ∼ 0.4 K. It was shown that Mn-based polymeric composite cured in aligned magnetic field presents a reinforcement of the MCE temperature hysteresis. Thus, the MCE value in aligned composite is less than the value of the MCE in the bulk MnAs. It was shown that the decreasing of linear size of MnAs grains in the polymeric composite leads to sharp decreasing of the MCE to value of 0.05 K. It was established that the optimal properties, such as giant MCE and low temperature hysteresis, are found for composite hardened under pressure of 10 kBar. In this composite an increase of reversible MCE (compared to the bulk MnAs) till to the value of ΔT ∼ 1.2K was observed.
Vibronic interaction as main reason of magnetic ordering in insulating manganites R1–xAxMnO3
Authors: Gonchar Liudmila , Nikiforov Anatoliy
Published: July 2018

The model of orbitally dependent magnetic structure of charge ordered insulated manganites is proposed. The model is semi-phenomenological. It allows using a few parameters to describe possible magnetic structures of compounds. The experimental crystal structure of compounds also could be taken into account. The compounds LaMnO3, La1/2Ca1/2MnO3, La1/3Ca2/3MnO3, BiMnO3 are considered.
Strain effect on resistivity of La0.7Ba0.3MnO3 thin film
Authors: Shaikhulov Timur A. , Shakhunov Valery A. , Demidov Victor V. , Ovsyannikov Gennady A. , Andreev Nikolay V. , Pestun Anna E. , Preobrazhensky Vladimir L.
Published: July 2018

A complex study of the dc and magnetic characteristics of epitaxial manganite films La0.7Ba0.3MnO3 (LBMO) was carried out under conditions of the crystal structure tension caused by a mismatch between the parameters of the LBMO crystal and the substrate. The epitaxial thin films with the thickness 150 nm were grown by laser ablation at T=700-800C under pure oxygen pressure 0.3-1 mbar. The substrates (001)LaAlO3, (001)SrTiO3, (110)NdGaO3, (001)[(LaAlO3)0.3+(Sr2AlTaO6)0.7] (LSAT) are used. It is shown that the temperature dependence of the film resistance in the low-temperature region does not depend on the film strain and it is in good agreement with the calculation that takes into account the interaction of carriers with magnetic excitations in the presence of strongly correlated electron states. The study of the of ferromagnetic resonance indicated the inhomogeneity of the ferromagnetic phase in LBMO films and an increase in the width of the FMR line with temperature decreasing.
Ab-initio study of electronic and magneto-optical properties of InAs:Mn
Authors: Gan’shina Elena , Kulatov Erkin , Golik Leonard , Kun’kova Zoya , Uspenskii Yurii , Zykov Georgy , Yuan Ye , Zhou Shengqiang
Published: July 2018

Energy difference between the ferromagnetic and antiferromagnetic collinear orderings has been calculated for the uniform and dimer Mn-pair geometries in order to find the ground state distribution of the Mn atoms in InAs host. We find the preference of the dimer ferromagnetic configuration of Mn dopants and an importance of optimizing the atomic site positions. The frequency-dependent optical and magneto-optical properties, namely the dielectric tensor (on-and off-diagonal components), the electron energy loss spectra, and the transversal Kerr effect (TKE), are calculated. Calculated TKE resonance in In1-xMnxAs (x=0.0625) is found to be in good agreement with corresponding experimental magneto-optical spectra. The origin of the large TKE is discussed.
Magnetic properties of Pb1-x-ySnxVyTe alloys
Authors: Skipetrov Evgeny , Konstantinov Nikita , Skipetrova Liudmila , Knotko Alexander , Slynko Vasily
Published: July 2018

We study the field and temperature dependences of the magnetization (B≤7.5 T, T=2.0-75 K) of samples from a single crystal Pb1-x-ySnxVyTe (x=0.08, y=0.01) ingot synthesized by the Bridgman method. It is established that the magnetization of the samples contains two main contributions: the Brillouin-type paramagnetism of vanadium ions and the diamagnetism of the crystal lattice. Experimental field and temperature dependences of the magnetization are discussed in the framework of a theoretical model of electronic structure rearrangement in Pb1-x-ySnxVyTe with doping and approximated as the sums of two terms based on the modified Brillouin functions for vanadium ions in the V3+ and V2+ states. The concentrations of magnetically active vanadium ions in two different charge states with increasing impurity concentration along the ingot are determined.
Electronic and magneto-optical properties of ZnO:Co
Authors: Kulatov Erkin , Novodvorskii Oleg , Lotin Andrey , Rylkov Vladimir , Gan’shina Elena , Shevyakov Dmitrii , Tugushev Victor , Uspenskii Yurii
Published: July 2018

High-quality ZnO:Co thin films were synthesized on the sapphire (0001) substrates by pulsed laser deposition. XRD result reveals that the Zn1-xCoxO films are of wurtzite-type crystal structure with x up to x = 0.35. The structural, optical and magnetic properties of ZnO:Co thin films are studied by experiments and theoretical calculations. Electronic structure of ZnO:Co with native defects are studied by the first-principles density functional theory. The experimental data and theoretical data have demonstrated quite good agreement. The optical and magneto-optical properties, namely, on-and off-diagonal conductivity tensor and the transversal Kerr effect (TKE), are calculated for comparison with available experimental data. The origin of observed TKE peaks is discussed..
Influence of oxygen vacancies on magnetic and transport properties of thin Zn1-xCoxOy films
Authors: Lotin Andrey A. , Kuz’mina Alina S. , Novodvorsky Oleg A. , Parshina Liubov S. , Khramova Olga D. , Mikhalevsky Vladimir A. , Cherebilo Elena A. , Shneider Alexander G. , Perov Nikolay S. , Makarova Liudmila A.
Published: July 2018

The features of the structural, transport and magnetic properties of thin Zn1-xCoxOy films (x=0-0.45), fabricated on С-sapphire substrates by the pulsed laser deposition method are studied. It is found that the transport and ferromagnetic properties of the wurtzite Zn1-xCoxOy films nonmonotonously depend on Co concentration at room temperature. For the Zn0.87Co0.13Oy film, the strongest ferromagnetic signal is observed that is caused by formation of the greatest number of metallic Co clusters. A further increase of doping impurity concentration in the films leads to the oxidation of metallic Co and formation of the paramagnetic Co3O4 phase, in consequence of which the ferromagnetic signal subsides.
Connection of thermopower, magnetothermopower with resistivity and magnetoresistance in manganites with Nd and Sm
Authors: Koroleva Luidmila , Batashev Ivan , Morozov Artem , Balbashov Anatolii , Szymczak Henryk , Slavska-Wanniewska Anna
Published: July 2018

Thermopower, magnetothermopower resistivity and magnetoresistance of single crystal samples Re(1-x)SrxMnO3 (0 ≤ x ≤ 0.3, Re = Nd, Sm) were studied in wide temperature interval, included the Curie temperature TC. Giant maxima of resistivity and thermopower, very big negative magnetothermopower and magnetoresistance were found in TC region. So, a giant maximum of thermopower in TC was found, which suppressed by magnetic field. Simultaneous magnetic field destroys magneto-impurity states – ferrons as evidenced the maxima resistivity and magnetoresistance in TC Hence it follows that giant thermopower in manganites are produced by ferrons and its value is set by the quantity of impurities, that is the concentration of impurities and the volume of sample.
Optical spectroscopy of ErFe3(BO3)4: detection of phase transitions and crystal-field levels of the Er3+ ground multiplet
Authors: Erofeev Dmitry , Jablunovskis Artjoms , Chukalina Elena
Published: July 2018

High-resolution spectra of oriented ErFe3(BO3)4 single crystals are registered in the spectral range 500 – 8000 cm-1 at various temperatures (4 – 470 K). The temperature behaviour of the phonon mode at 976 cm-1 allowed us to register a structural phase transition at TS=431 K. The energies of crystal-field levels of the ground 4I15/2 and the first excited 4I13/2 multiplets of the Er3+ ion are determined in the paramagnetic state of ErFe3(BO3)4. The exchange splitting of the ground Kramers doublet in the magnetically ordered state was found to be Δ0=6.3±1 cm-1. The interference occurring due to birefringence in the single crystals was also registered. The temperature dependence of the position of the maximum of the interference band demonstrates two anomalies, at TN and TS, associated with the phase transitions in ErFe3(BO3)4.