bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a technological platform for teaching and training in competitive programming contests
Authors: Lázaro Carrillo G Y , Delgado León A M , Vera Contreras M J , Vera-Rivera F H 
Published: November 2019

Abstract
The competitive programming contests are competitions where the programming capacity and algorithm of the participants are measured. The objective of this work was to develop and implement a framework to formalize the working methodology of the competitive programming study group of the Universidad Francisco de Paula Santander and to develop a web-based training platform to monitor the work carried out within the study group. The intention with this platform is to give the students the tools they need to carry out their training, from the platform the student can study, can practice, can compete, and can improve their skills both in competitive programming, as well as in areas of programming and computer science. This work was carried out following an iterative methodology composed of the following phases: initially, the project has been formalized, analysis of the problem, preliminary details, and formation of the state of the art and theoretical reference. Then, the initial state of the group is diagnosed, a solution is proposed. After refining this solution proposal. Once implemented, information and metrics are gathered and the results are analyzed, already with a functional framework and a web platform, to detect problems and improvements, restarting the phases, for improving in each step those aspects that can be enhanced. The results obtained in the national and international contest have improved considerably and the participation and satisfaction of the students who are part of the study group were increased. The technological platform developed constitutes a confluence point for the study group, and a clear guideline to follow to advance in the process of continuous improvement that allows the university to achieve the best results in national and international programming competitions.
Bloch lines in thin films with perpendicular magnetic anisotropy and intermediate quality factor
Authors: Izmozherov I M , Zverev V V , Baykenov Erlan Zh. 
Published: November 2019

Abstract
Bloch lines (BLs) are linear topological defects of magnetic domain walls structure, studied well for bubble domain materials. We investigate its structure and role in magnetization reversal for thin ferromagnetic films with perpendicular magnetic anisotropy and intermediate quality factor. We observe vertical BLs with Bloch points and U-shaped structures with vertical and horizontal parts in three-dimensional micromagnetic simulations for Q = 0.34. Also we suggest analytical model functions, describing 3D magnetization distribution in domain walls with BLs.
Solitons in The Domain Structure of an Easy-Axis Ferromagnet
Authors: Kiselev V V , Raskovalov A A 
Published: November 2019

Abstract
We obtain new solutions of the Landau-Lifshitz model by the inverse scattering technique. They describe solitons strongly associated with the domain structure of an easy-axis ferromagnet. Solitons serve as elementary carriers of macroscopic shifts of the structure and are, under certain conditions, nuclei of the magnetic reversal of a material. We show, that the inhomogeneous elliptic precession of magnetization in a soliton core leads to oscillations of the neighbouring domain walls of the structure. We study the behavior of immobile solitons in the domain structure, which are more simple to observe in experiment. We investigate the structure of solitons near the boundaries of their existence.
Magnetic component of mixing enthalpy for BCC Fe-Cr alloys: ab initio based model
Authors: Mirzaev D A , Mirzoev A A 
Published: November 2019

Abstract
The standard magnetic model in the current CALPHAD modelling is based on the Inden–Hillert–Jarl model and can be used to ferromagnetic and antiferromagnetic alloys. In this work, we demonstrate that this model can also be applied to alloys with more complicated forms of magnetism. The concept of ‘effective magnetic moment’ has been introduced as a measure of the maximum magnetic entropy. To calculate this quantity, it is necessary to know the local magnetic moments on the atoms of the components. A case study on the Fe –Cr system has been performed by Density Functional Theory (DFT) formalism at 0 K. It is shown that the CALPHAD modelling using the concept of effective magnetic moment leads to good agreement with the data of ab-initio modeling of the magnetic contribution to the mixing energy of Fe-Cr alloys.
Two types of 3-d metals nanowires: synthesis, structure and properties
Authors: Zagorskiy D , Doludenko I , Zhigalina O , Ivanov I , Muslimov A , Cherkasov D , Biziaev D , Bukharaev A 
Published: November 2019

Abstract
Matrix synthesis based on etched-track membranes was used for fabrication of two type of nanowires (NWs) – homogeneous (alloys – Fe-Co and Fe-Ni) and heterogeneous – layered NWs (Ni/Cu and Co/Cu). Parameters of galvanic process and features of electrodeposition were determined. X-ray analysis demonstrated the two-phase structure of alloys with low concentration of Fe and step-type changing of cell-parameter with changing of metals concentration ratio in alloy NWs. Topography of NWs was determined by SEM: NWs’ diameter were higher than pores size due to metal oxidation or expansion. Elemental analysis demonstrated that composition of Fe-Co NWs is equal to composition of electrolyte, while for Fe-Ni Fe concentration in NWs is higher; this difference increases with concentration of Fe. TEM allows to evaluate the length of metal segments in layer NWs, to estimate their concentration (pure Cu and mixed Co or Ni). Magnetic-Force microscopy allows to correspond structure and domain size. External field could change magnetization, but only partly – due to mutual influence of NWs.
Magnetism of amorphous Dy-Tb-Co-type films
Authors: Balymov K G , Kudyukov E V , Vas’kovskiy V O , Adanakova O A , Kulesh N A , Stepanova E A , Rusalina A S 
Published: November 2019

Abstract
In this work a systematic study of magnetic properties of amorphous TbxCo100-x and DyxCo100-x films is presented. In a composition range 15 < x < 40 at. %, temperature dependencies of spontaneous magnetization in a temperature interval 5 – 300 K as well as low-temperature 5 K hysteresis loops in magnetic field up to ±70 kOe have been obtained. We demonstrated, that the experimental results can be interpreted in a framework of a model considering a variable sperimagnetic cone angle of rare earth atoms up to 150°. A series of Tb-Dy-Co films with a composition close to Laves phase has been obtained. We demonstrated that the variation of rare earth content with Co content fixed does not lead to a systematic lowering of magnetic hysteresis.
The Kondo effect in 2D electron gas of magnetically undoped AlGaN/GaN high-electron-mobility transistor heterostructures
Authors: Chumakov N K , Chernykh I A , Davydov A B , Ezubchenko I S , Grishchenko Yu V , Lev L L , Maiboroda I O , Strocov V N , Valeyev V G , Zanaveskin M L 
Published: November 2019

Abstract
Unusual observation of the Kondo effect in two-dimensional electron gas (2DEG) of magnetically undoped AlGaN/GaN high-electron-mobility transistor heterostructures is reported. The temperature-dependent zero-field resistivity data exhibited an upturn below 120 K, while the standard low-temperature weak-localization behaviour was revealed at T → 0. Magnetotransport characterization was carried out in the magnetic fields up to 80 kOe, applied perpendicular to the 2DEG plane, in the temperature range 1.8 ÷ 300 K. Negative low-temperature magnetoresistance with a magnitude of order of 1 % was detected. The data set is analysed in the frame of the multichannel Kondo model for d0-magnetic materials.
Experimental and numerical analysis of magnetic susceptibility of the tetranuclear heterometallic SMM complexes [Me2
IIFe2
III(L)4(OH)2⋅EtOH)2⋅(Et2O)2], Me = Co, Ni with dicubane structure
Authors: Starichenko D , Shvachko Yu , Anokhin A , Kuznetsov A 
Published: November 2019

Abstract
Magnetic susceptibilities of the two isostructural heterometallic complexes, [Me2
IIFe2
III(L)4(OH)2,(EtOH)2,(Et2O)2], Me = Co, Ni, with triketonate ligands L = dianion of 1,1,1,7,7,7-hexa-fluoroheptane-2,4,6-trione, were studied experimentally and theoretically. Extended theoretical analysis included a phenomenological approach as well as quantum calculations in several numerical schemes. Magnetic ground states of Co2
IIFe2
III(L)4 and Ni2
IIFe2
III(L)4 complexes were resolved as an interplay of two intrinsic superexchange interactions with the constants J
FeFe and J
CoFe/J
NiFe. The first system was described by two non interacting AFM-coupled pairs Co-Fe with J
CoFe = - 4.2 cm−1 and zero-field splitting parameter D = -0.15 cm−1. The second one revealed the ferromagnetic coupling between the AFM dimers, J
NiFe = -12.1 cm−1, J
FeFe = 1.3 cm−1 and D = -0.5 cm−1.
The influence of the interlayer on the magnetic and structural properties of three-layer systems
Authors: Shalygina E , Kharlamova A , Efremova S , Makarov A , Kurlyandskaya G , Svalov A 
Published: November 2019

Abstract
This article is dedicated to the influence analysis of the thickness and composition of nonmagnetic intermediate layers, t
NM, on the magnetic and structural properties of Co/Mo/Co, Co/Si/Co, Co/Bi/Co and Fe1/PDP/Fe2 thin-film systems, as well as comparing the mechanisms of exchange interaction between ferromagnetic, FM, layers through NM spacers. The thicknesses of Co layers are equal to 5.0 nm and the thickness of Fe layers is varied from 14.0 to 50.0 nm. The thickness of NM layers, depending on its composition, is changed from 0.2 to 50.0 nm. It is found that the hysteresis loops for some samples measured in a magnetic field applied parallel to the easy magnetization axis have a rectangular form and for others – more complex two-step ones. The saturation field, HS, of Co/Mo/Co, Co/Si/Co and Co/Bi/Co samples oscillates in magnitude. These data are explained by the presence of exchange coupling between the Co layers through a NM spacer. Fe1/PDP/Fe2 samples have a two-step hysteresis loops, which at t
PDP ≥ 10 nm are explained by the exchange coupling between the Fe layers through the PDP layer, and at t
PDP > 10 nm - by the magnetostatic interaction between the Fe layers due to the difference in their thickness.
Magnetic properties of GdCo-Al2O3 composite films
Authors: Gorkovenko A N , Lepalovskij V N , Vas’kovskiy V O 
Published: November 2019

Abstract
The purpose of this work was to synthesize and study magnetic properties of composite films consisting of Gd-Co ferrimagnetic system and Al2O3 dielectric matrix. GdCo-Al2O3 films of different composition were synthesized by magnetron co-sputtering of Gd, Co, and Al2O3 targets in an Ar atmosphere. Investigation of magnetic properties was carried out using a vibrating sample magnetometer in the temperature range from 10 to 300 K. The obtained results showed that in the composite system with a volume of dielectric material exceeding 50% a superparamagnetic state is realized, indicating granular microstructure. In this case, the granules show signs of ferrimagnetic ordering.
Magnetic properties of Fe-Bi films
Authors: Patrin G S , Yakovchuk V Yu , Yarikov S A , Shiyan Ya G , Furdyk V P , Patrin K G 
Published: November 2019

Abstract
In the paper the results of experimental studies of film structures in the Fe-Bi system are presented. By the method of electron magnetic resonance, it is shown that for bilayer structures the magnetic state depends on the order of deposition of the magnetic and non-magnetic layers. In the three-layer structures, the effect of exchange bias was found, the magnitude of that depends on the thickness of the bismuth layer.
Non-equilibrium vortex annealing of structural disorder in the critical relaxation of diluted two-dimensional XY-model
Authors: Popov Ivan S , Popova Anna P , Prudnikov Pavel V 
Published: November 2019

Abstract
The study of the effects of aging in the non-equilibrium critical relaxation of a two-dimensional XY-model with a non-equilibrium vortex annealing of structural disorder has been carried out. Two-time dynamic dependencies of the spin-spin and defect-defect autocorrelation functions C
SS (t,t
w) and C
DD (t,t
w) are obtained for the entire Berezinskii low-temperature phase T < T
BKT(p), for a wide range of waiting times t
w and spin concentrations p. Near the BKT phase transition point T
BKT (p), the dynamic dependencies C
DD(t,t
w) become uniform with time. However, with a decrease in temperature in the low-temperature phase T < T
BKT (p), this relaxation uniformity breaks down, and C
DD(t,t
w) does not exhibit canonical aging properties. The formation of a declining family of dynamical scaling curves is clearly observed at large observation times t – t
w which may indicate the presence of an asymptotic scaling dependence of C
DD (t, t
w).
Temperature dependence of the interphase interaction energy of core/shell nanoparticles
Authors: Anisimov S V , Afremov L L , Petrov A A 
Published: November 2019

Abstract
Within the framework of the Ising model, in the direct exchange interaction approximation by the “average spin” method, the constant of the interphase exchange interaction A(T), which determines the exchange bias field, is estimated. It was shown that A(T) ~ e(−T/T
0), where the characteristic temperature T
0 is determined by the constant of the exchange interaction between the atoms of the core and the shell.
The role of the semiconductor layer in the exchange-bias film structure of CoNi / Si / FeNi / Si with a spin spring effect
Authors: Kobyakov A V , Turpanov I A , Patrin G S , Yushkov V I , Yarikov S A , Volochaev M N , Zhivaya Ya A 
Published: November 2019

Abstract
CoNi / Si / FeNi / Si structures were synthesized by ion-plasma sputtering. A negative hysteresis loop bias was detected at the thickness of the silicon layer was less than 2 nm and the temperature was less than 100 K. A positive hysteresis loop bias was detected at the thickness of the silicon layer was more than 2 nm and the temperature greater than 100K.
Microwave refraction coefficient in nanocomposites and nanostructures in magnetic field
Authors: Perov D , Rinkevich A , Nemytova O 
Published: November 2019

Abstract
Microwave refraction coefficient is studied for two types of composites and for metallic (CoFe)/Cu nanostructures. Nanocomposites of the first type are prepared on the base of artificial opal matrices with embedded particles of nickel-zinc ferrite and metallic cobalt. The introduced particles are sized from 5 to 60 nm. The composite material of the second type is prepared of permalloy flakes sized about 2 – 50 μm placed into epoxy amine matrix. At frequencies of centimeter and millimeter waveband the magnetic field dependences of transmission and reflection coefficients have been measured. The complex refractive coefficients are obtained as a function of magnetic field. The complex refraction coefficient can be expressed via the effective dielectric permittivity and magnetic permeability. Analysis of magnetic field dependences of refraction coefficient shows that strong variations are observed near ferromagnetic resonance. For metallic nanostructures there are also variations of the refraction coefficient caused by giant magnetoresistive effect.
The reason of occurrence of a longitudinal residual induction of steel spindle after circular magnetization
Authors: Reutov Yu 
Published: November 2019

Abstract
A special attention is paid to the possibility of appearance of a longitudinal residual magnetic flux leakage (MFL) field in the tested ferromagnetic spindle after its circular magnetization. The reasons of appearance of this field and experimental verification of the interpretation are given. When the occurrence of such field is unacceptable, the spindle has to be demagnetized.
Magnetic non-destructive testing of residual stresses in low carbon steels
Authors: Stashkov A , Nichipuruk A , Kuleev V , Schapova E 
Published: November 2019

Abstract
A new calibration-free magnetic method and a measuring system for residual stresses monitoring in low carbon steels have been developed. The method is based on the fact that during the action of compressive stresses in the material an “easy plane” magnetic texture appears. Magnetic texture affects the processes of magnetization reversal of the testing object in such a way that two or three maxima on the curves of differential μd(H) or reversible μrev(H) magnetic permeabilities appear. The fields of the maxima are associated with the magnetoelastic field and residual stresses. To increase the reliability of testing results and simplify the evaluation of residual stresses in testing objects, it was proposed to use the method of subtracting experimental μd(H) curves measured in the zones of action of compressive stresses and in the object under test without stresses. The method can also be used to estimate residual tensile stresses that are the most dangerous for steel structures.
Highly effective system for excitation and reception of Lamb waves in ferromagnets
Authors: Mikhailov A V , Gobov Yu L , Smorodinskii Ya G 
Published: November 2019

Abstract
The paper presents the concept of a highly efficient system for excitation and reception of Lamb waves in ferromagnets. Methods for creating large polarizing fields allowing to increase the efficiency of generation and reception of Lamb waves in ferromagnets and the principles of unidirectional electromagnetic-acoustic transducers are proposed. The results obtained in this work can be used in the development of devices for non-destructive testing of the long ferromagnetic objects.
The influence of zero-to-tension loading on magnetic and acoustic properties of 08G2B hot-rolled steel
Authors: Gorkunov E S , Povolotskaya A M , Zadvorkin S M , Putilova E A , Mushnikov A N , Bazulin E G 
Published: November 2019

Abstract
The paper reports on the results of studying the effect of the number of zero-to-tension loading cycles, with an amplitude approximately corresponding to conventional yield strength, on the acoustic and magnetic parameters of the 08G2B hot-rolled pipe steel, including its longitudinal and transverse magnetostrictions. The parameters uniquely varying with the number of cycles have been determined, and this principally enables these parameters to be used for the development of nondestructive methods of testing fatigue degradation in the material of structures made of the steel under study.
Terahertz-infrared spectroscopy of single crystalline m-type hexaferrite BaTixFe12-xO19
Authors: Yegiyan S R , Alyabyeva L N , Torgashev V I , Vinnik D A , Gudkova S A , Prokhorov A S , Dressel M , Gorshunov B P 
Published: November 2019

Abstract
We have studied polarization-dependent broad-band dielectric response of single-crystalline Ti-substituted barium hexaferrites BaTixFe12-xO19, x=0.64., 0.75, 1.1, in the frequency range from 10 to 8000 cm−1 and at temperatures from 5 to 300 K. In addition to a rich set of phonon resonances located at frequencies from 90 to 800 cm−1 we observed an unusual low-energy response (terahertz region, 10-100 cm−1) stemming from two different effects: relaxational process and second order spin-orbit coupling in Fe2+ ground state, that may set up new prospects for doped hexaferrites in terahertz technologies.
Concept of using composite multiferroic structure magnonic crystal - ferroelectric slab as memory unit
Authors: Matveev O , Morozova M , Romanenko D 
Published: November 2019

Abstract
In the present work, it is proposed to use as a memory cell with random access a new type of memristor - a multiferroic wave memristor based on structures type magnonic crystal-ferroelectric. Main feature of propagating excitations trough such structure is band gap formation: Bragg band gap that position in spectrum depends on the polarization of ferroelectric. Thus, information from ferroelectric is read as a result of signal transmission / attenuation at frequency of band gap. In present work theoretical model of spin waves propagating in structure magnonic crystal-ferroelectric is developed. Results of an experimental study of the propagation of spin-wave excitations in such structure are given.
Magnetic properties of Ho0.9Er0.1Fe3(BO3)4
Authors: Gudim Irina , Demidov Andrey , Eremin Eugene , Temerov Vladislav , Shukla Dinesh 
Published: November 2019

Abstract
The magnetic properties of Ho0.9Er0.1Fe3(BO3)4 ferroborate with the competing Ho–Fe and Er–Fe exchange couplings have been experimentally and theoretically investigated. The measured magnetic characteristics (Ma,c
(B), χa,c
(T)) and observed features are interpreted using a single theoretical approach based on the molecular-field approximation and calculations within the crystal-field model of the rare-earth ion. Interpretation of the experimental data includes determination of the crystal-field parameters for Ho3+ and Er3+ ions in Ho0.9Er0.1Fe3(BO3)4 and parameters of the Ho–Fe and Er–Fe exchange couplings.
Effects of long storage in La-Sr manganites with pared divalent and quadrivalent substituents for manganese
Authors: Karpasyuk V K , Badelin A G , Derzhavin I M , Estemirova S Kh , Merkulov D I 
Published: November 2019

Abstract
The results of investigation on the ageing of ceramic manganites La1-cSrcMn0.90Ni0.05Ge0.05O3+γ and La1-cSrcMn0.90Zn0.05Ti0.05O3+γ (c = 0.15, 0.17, 0.19) during long-term storage at normal conditions are presented. Unit cell volume of all manganites having rhombohedral structure decreased over time. The width of X-ray diffraction reflexes from (Ni,Ge)-compositions varied irregularly within the measurement error, and the width of reflexes from (Zn,Ti)-contained manganites decreased significantly. Magnetization of all samples increased in the end of storage period. Curie point of compositions with c > 0.17 exhibited some trend of increase. Ageing leaded to the lowering of “metal-semiconductor” transition temperature in (Ni,Ge)-substituted manganites. (Zn,Ti)-contained compositions showed only semiconductor behavior in investigated temperature range from 100 to 300 K, and the changes of their magnetic parameters were most considerable. The increase in magnetization and Curie point reached 7.5 % and 11 %, respectively. Possible mechanisms of ageing in considered materials are discussed in terms of oxidation processes, formation of microinhomogeneities and relaxation of internal stresses.
Magnetoelectric structure with integrated current carrying electrodes
Authors: Burdin D A , Saveliev D V , Fetisov Yu K , Ekonomov N A , Chashin D V 
Published: November 2019

Abstract
Various methods of magnetoelectric effect excitation in a composite structure consisting of ferromagnetic and piezoelectric layers are investigated and compared, such as: by ac magnetic field of electromagnetic coil, by ac current flowing through external conductive strip, by ac current flowing through the ferromagnetic layer, and by as current flowing through electrode of the piezoelectric layer. It is shown that ac current flowing through the ferromagnetic layer effectively excites both linear and nonlinear magnetoelectric effects due to absence of demagnetization. Specific dependence of the voltage harmonics on the permanent magnetic field under the structure excitation by ac current are observed and explained.
Thickness dependence of conductivity in Bi2Se3 topological insulator
Authors: Chistyakov V V , Domozhirova A N , Huang J C A , Marchenkov V V 
Published: November 2019

Abstract
The electrical resistivity of thin films of a topological insulator of Bi2Se3 with a thickness of 10 nm to 75 nm, single crystal of Bi2Se3 with thickness of 0.65 mm in the temperature range from 4.2 to 300 K was measured. A size effect in the electrical conductivity of Bi2Se3 films was observed, i.e. linear dependence of the conductivity of the sample on its inverse thickness. It was suggested that similar effects should be observed in other TIs and systems with non-uniform distribution of direct current over the cross section of the sample.