Wyniki wyszukiwania - Biblioteka Nauki

1

On the magnetization-based Lagrangian methods for 2D and 3D viscous flows. Part 1 - theoretical background

100%

Styczek A. , Szumbarski J.

Journal of Theoretical and Applied Mechanics

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2002

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tom Vol. 40 nr 2

339-355

EN

The paper presents the background of an alternative formulation of the Navier-Stokes equation using a variable called the magnetization. Several variants of governing equations, based on different choices of a particular gauge transform, are discussed. The remaining part of the paper is devoted to the formulation of a Lagrangian approach to 2D and 3D viscous flows. First, the carrier of the magnetization (the magneton) is defined and the corresponding induction law is derived. The instantaneous velocity field is constructed as a superposition of contributions from a large set of magnetons and a uniform stream. An essential feature of the method is a one-time-step operator splitting, consisting in the consecutive solution of three sub-problems: generation of the magnetization on solid boudaries, advection-diffusion of the magnetization and sretching.

PL

W artykule przedstawione jest sformułowanie problemu granicznego dla równań Naviera-Stokesa z użyciem tzw. pola magnetyzacji. Sformułowanie nie jest jednoznaczne, lecz wiąże się z przyjętą transformacją cechowania. Rozważane są różne postacie tej transformacji i dokonuje się wyboru odpowiednich wariantów. Pole magnetyzacji przedstawione jest w formie lagrangeowskiej. Wprowadza się cząstki będące źródłami tego pola i określa się związane z ich zbiorem pole prędkości. Cząstki magnetyzacji (zwane magnetonami) poruszają się w indukowanym polu prędkości, wykonują ruch losowy odpowiadający dyfuzji i podlegają przekształceniu w sposób opisany członem źródłowym (tzw. stretching). Warunek brzegowy sformułowany na opływanym ciele jest realizowany przez tworzenie w każdej chwili nowych cząstek ulokowanych w bliskim otoczeniu powierzchni ciała.

2

The low temperature magnetic properties of potassium holmium double tungstate

100%

Borowiec M. , Khatsko E. , Dyakonov V. , Rykova A. , Majchrowski A. , Zayarnyuk T. , Barański M. , Żmija J. , Szymczak H.

Open Physics

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2011

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tom 9

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nr 1

260-262

EN

The magnetic investigations of potassium holmium double tungstate KHo(WO4)2 have been performed. The results of measurements of magnetic susceptibility and magnetization as a function of both temperature (T = 0.5–100 K) and magnetic field (up to 2 T) are presented.

3

Magnetic Properties of Steel Ball Samples, Investigated before and after Nitriding

100%

Fuks H. , Kaczmarek S. M. , Leniec G. , Michalski J. , Kucharska B. , Wach P.

Archives of Metallurgy and Materials

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2018

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tom Vol. 63, iss. 3

1235--1242

EN

Group of steel balls with different chemical composition, diameters and nitriding treatment parameters were investigated with using magnetic resonance and magnetization methods. Emerging nitrided regions consists of diffusion and surface layer of iron nitrides. The thickness of the individual layers depends on the type of steel and process parameters. Resonance signal shape and position were successfully described in the ferromagnetic resonance regime expected for dense iron magnetic system. Influence of the sample size, thermal treatment and carbon content on the absorption signal has been analyzed. Significant magnetic anisotropy has been revealed, as well as non-usual increasing of the magnetization as a function of temperature. It suggests, that overall antiferromagnetic ordering, destroyed by thermal movement, lead to increasing of the ferromagnetic region.

4

Magnetoresistance effect in layered cobaltite Sr0.9Y0.1CoO2.63

100%

Bushinsky M. , Tereshko N. , Mantytskaya O. , Fedotova V. , Lanovsky R.

Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej

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2018

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tom Nr 13

105--114

EN

The structure and the magnetic and magnetotransport properties of the perovskite sample Sr0.9Y0.1CoO2.63 have been studied using different diffraction methods and magnetization and conductivity measurements. Synchrotron X-ray diffraction shows that the sample is structurally two-phase. The majority phase has a tetragonally distorted unit cell and is described by the space group I4/mmm. A very strongly broadened superstructure peak observed at small angles in X-ray diffraction patterns at temperatures below 400 K are explained by the existence of a monoclinic phase with large unit cell whose phase fraction is much smaller than that of the tetragonal phase, but which is dominant in the sample Sr0.8Y0.2CoO2.65. The spontaneous magnetization strongly increases with increasing the Y content up to 20% due to formation of the monoclinic phase. The magnetic structure is predominantly antiferromagnetic G-type with magnetic moments 1.5 μB in the layers of CoO6 octahedra and 2 μB in the anion-deficient CoO4+γ layers. The electrical conductivity of the sample Sr0.9Y0.1CoO2.63 has semiconducting character. The magnetoresistance reaches 58% for the field B = 14 T at 5 K and decreases strongly with the increasing temperature and Y content.

PL

Struktura i właściwości magnetyczne i magnetotransportowe perowskitu Sr0.9Y0.1CoO2.63 zostały zbadane przy użyciu różnych metod dyfrakcyjnych oraz pomiarów namagnesowania i przewodnictwa. Dyfrakcja rentgenowska mierzona na synchrotronie pokazuje, że próbka ma strukturę dwufazową. Główna faza ma tetragonalnie zniekształconą komórkę elementarną i jest opisana przez grupę przestrzenną I4 /mmm. Pik o bardzo mocno poszerzonej superstrukturze obserwowano pod niewielkimi kątami w dyfraktogramach rentgenowskich w temperaturach poniżej 400 K i jest związany z istnieniem fazy monoklinowej o dużej komórce elementarnej, której frakcja fazowa jest znacznie mniejsza niż faza tetragonalna, ale która jest dominujący w próbce Sr0.8Y0.2CoO2.65. Spontaniczne namagnesowanie silnie wzrasta wraz ze wzrostem zawartości Y do 20% z powodu tworzenia się fazy monoklinowej.

5

Structure and some magnetic properties of (BiFeO3)x-(BaTiO3)1-x solid solutions prepared by solid-state sintering

100%

Kowal K. , Kowalczyk M. , Czekaj D. , Jartych E.

Nukleonika

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2015

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tom Vol. 60, No. 1

81--85

EN

This paper presents the results of the study on structure and magnetic properties of the perovskite-type (BiFeO3)x-(BaTiO3)1-x solid solutions. The samples differing in the chemical composition (x = 0.9, 0.8, and 0.7) were produced according to the conventional solid-state sintering method from the mixture of powders. Moreover, three different variants of the fabrication process differing in the temperatures and soaking time were applied. The results of X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and vibrating sample magnetometry (VSM) were collected and compared for the set of the investigated materials. The structural transformation from rhombohedral to cubic symmetry was observed for the samples with x = 0.7. With increasing of BaTiO3 concentration Mössbauer spectra become broadened refl ecting various confi gurations of atoms around 57Fe probes. Moreover, gradual decreasing of the average hyperfi ne magnetic fi eld and macroscopic magnetization were observed with x decreasing.

6

Magnetoresistance peculiarities and magnetization of materials with two kinds of superconducting inclusions

100%

Shevtsova O. N.

Materials Science Poland

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2015

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tom Vol. 33, No. 1

73--81

EN

Low-temperature properties of a crystal containing type I superconducting inclusions of two different materials have been studied. In the approximation assuming that the inclusions size is much smaller than the coherence length/penetration depth of the magnetic field, the theory of magnetoresistance of a crystal containing spherical superconducting inclusions of two different materials has been developed, and magnetization of crystals has been calculated. The obtained results can be used for correct explanation of the low temperature conductivity in binary and more complex semiconductors, in which precipitation of the superconducting phase is possible during the technological processing or under external impact.

7

Structural and magnetic studies on Co-Zn nanoferrite synthesized via sol-gel and combustion methods

100%

Vara Prasad B. B. V. S. , Ramesh K. V. , Srinivas A.

Materials Science Poland

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2019

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tom Vol. 37, No. 1

39--54

EN

Co–Zn nanocrystalline ferrites with chemical composition Co0.5Zn0.5 Fe2O4 were synthesized by sol-gel and combustion methods. The sol-gel method was carried out in two ways, i.e. based on chelating agents PVA and PEG of high and low molecular weights. In auto-combustion method, the ratio of citric acid to metal nitrate was taken as 1:1, while in sol-gel method the chelating agents were taken based on oxygen balance. All the three samples were studied by thermogravimetric and differential thermal analysis for the identification of phase formation and ferritization temperature. The synthesized samples were characterized by powder X-ray diffraction and FT-IR spectroscopy without any thermal treatment. The measured lattice constants and observed characteristic IR absorption bands of the three samples are in good agreement with the reported values showing the formation of a cubic spinel structure. The crystallite sizes of all samples were determined using high intensity peaks and W-H plot. Size-Strain Plot method was also implemented since two of the samples showed low crystallite sizes. The least crystallite size (5.5 nm) was observed for the sample CZVP while the highest (23.8 nm) was observed for the sample CZCA. Cation distribution was proposed based on calculated and observed intensity ratios of selected planes from X ray diffraction data. All structural parameters were presented using experimental lattice constant and oxygen positional parameter, and they correlated with FT-IR results. Magnetic measurements were carried out using vibrating sample magnetometer at room temperature to obtain the characteristic parameters such as saturation magnetization, coercivity, remanence, squareness ratio and Bohr magnetons. Among all, the sample synthesized via citric acid autocombustion method displayed a remarkably higher magnetization of 53 emu/g and the remaining two samples displayed low magnetization values owing to their smaller crystallite sizes.

8

Structure and some magnetic properties of (BiFeO3) x -(BaTiO3) 1− x solid solutions prepared by solid-state sintering

100%

Kowal K. , Kowalczyk M. , Czekaj D. , Jartych E.

Nukleonika

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2015

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tom 60

|

nr 1

81-85

EN

This paper presents the results of the study on structure and magnetic properties of the perovskite-type (BiFeO3)x-(BaTiO3)1−x solid solutions. The samples differing in the chemical composition (x = 0.9, 0.8, and 0.7) were produced according to the conventional solid-state sintering method from the mixture of powders. Moreover, three different variants of the fabrication process differing in the temperatures and soaking time were applied. The results of X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and vibrating sample magnetometry (VSM) were collected and compared for the set of the investigated materials. The structural transformation from rhombohedral to cubic symmetry was observed for the samples with x = 0.7. With increasing of BaTiO3 concentration Mössbauer spectra become broadened reflecting various configurations of atoms around 57Fe probes. Moreover, gradual decreasing of the average hyperfine magnetic field and macroscopic magnetization were observed with x decreasing.

9

On the magnetization-based Lagrangian methods for 2D and 3D viscous flows. Part 2 - numerical implementation and results

100%

Duszyński P. , Olszewski P. , Poćwierz M. , Styczek A. , Szumbarski J.

Journal of Theoretical and Applied Mechanics

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2002

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tom Vol. 40 nr 4

825-846

EN

The numerical implementation of the Lagrangian method using particles of the magnetization field (magnetons) has been considered. A detailed description of essential elements of the algorithm has been provided. The presentation has focused on computations of stretching, where a novel integral-based rather than point wise approach has been proposed. The results of test computations, carried out for viscous flows past 2D and 3D bodies, have been presented. Difficulties with obtaining stable large-time simulations have been encountered and discussed. It has also been shown that, in contrast to flows around solid bodies, the vortex dynamics in the absence of boundaries can be successfully simulated, however, some consistent remeshing technique may by necessary to achieve appropriate resolution.

PL

W tej części pracy przedstawiono realizację numeryczną i opis wyników wyznaczania ruchów cieczy lepkiej uzyskanych lagrangeowską metodą cząstek magnetyzacji. Podano szczegóły wyznaczenia członu źródłowego (tzw.stretching term). Zaproponowano szczególny nowy sposób postępowania związany z tym efektem. Praca zawiera wyniki symulacji opływów dwu i trójwymiarowych oraz dyskusję napotkanych trudności. Podano też wyniki symulacji ewolucji swobodnych struktur wirowych. Modelowanie takich struktur jest prostsze wobec braku warunku brzegowego.

10

Properties of GdFeAl ternary compound in two crystallographic structures

100%

Klimczak M. , Talik E. , Jarosz J. , Mydlarz T.

Materials Science Poland

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2008

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tom Vol. 26, No. 4

954--958

EN

Properties of the GdFeAl compound which crystallized in the cubic MgCu2-type structure as well as in hexagonal MgZn2-type structure were compared. The electrical resistivity, AC susceptibility and magnetization as a function of temperature revealed relatively high magnetic ordering temperature about 200 K. The differences in magnetization were observed for samples crystallizing in two different crystallographic structures. The magnetic moments measured at 4.2 K and up to140 kOe are very far from the magnetic moment value for free Gd ion. The magnetic moment values of cubic and hexagonal phases are 1.1 μB and 1.7μB, respectively.

11

Field-induced magnetization of a free-electron gas in thin films

100%

Balcerzak T.

Materials Science Poland

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2007

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tom Vol. 25, No. 2

447--451

EN

A free-electron model in thin film embeded in an external magnetic field is considered. Based on the paramagnetic susceptibility, a formula for magnetization of the electron gas in the uniform magnetic field is derived. Selected results are presented for the films with the thickness of several atomic planes, and with the electron density corresponding to copper.

12

Evaluation of Differences between Fe₃O₄ Micro- and Nanoparticles Properties

100%

Duriagina Z. , Tepla T. , Kulyk V.

Acta Physica Polonica A

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2018

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tom 133

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nr 4

869-872

EN

Small sizes of nanoparticles lead to the appearance of new unique functional properties. Under transition to nanosizes in metals and their compounds new specific characteristics appears. In this work, the microstructural and magnetic properties of Fe₃O₄ nanoparticles (Fe₃O₄-NP) have been compared with those of commercially available Fe₃O₄ microparticles (Fe₃O₄-MP) and detailed analysis of differences has been carried out. The synthesis of Fe₃O₄-NP was carried out by means of colloidal method performed without the use of surfactants. Commercial and synthesized particles were characterized using NTEGRA Prima (NT-MDT) atomic force microscope. For magnetic properties investigations we used the method of vibrating sample magnetometer.

13

Effects of low-level La doping and ageing on TlPb-1223 high T c superconductors

88%

Cigáň A. , Plesch G. , Škrátek M. , Kopčok M. , Maňka J. , Jurdák P. , Koňakovský A.

Open Physics

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2011

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tom 9

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nr 1

213-221

EN

Bulk samples of the nominal composition of (Tl0.6Pb0.5)(Sr0.8Ba0.2)2Ca2Cu3O8+δ−xLaO1.5 (x = 0–0.1) were prepared by using two-step process and their microstructure, T c values, and magnetization were studied. The samples consist of the Tl-1223 dominant phase with small Tl-1212 admixture, which increases with a rise of La content. Five years ageing and following oxygen annealing at 450°C and subsequently at 750°C have only a modest effect on T c values of the studied samples. Low-level La doping (x = 0:04) leads to an increase of T c values by about 2 K in comparison with undoped samples. Oxygen annealing at 750°C results in an increase in the volume magnetization hysteresis in low applied magnetic fields and rise of critical current density at zero magnetic field and 77 K. This effect is most pronounced for the low La doped sample with x = 0.04. Changes of the induced voltage, U originating in the Meissner effect and of its harmonics in dependence on temperature were measured and used for characterization of the temperature distribution of inter-grain junctions.

14

The influence of self-doping of stibnite ore with impurities on the preparation, heat capacity, magnetic and transport properties of tetrahedrite Cu12Sb4S13

88%

Chen Y. , Li L. , Zhang Q. , Zhang C. , Hirai S.

Materials Science Poland

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2020

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tom Vol. 38, No. 3

484-492

EN

Stibnite mineral (mainly Sb2S3) has been employed for the synthesis of tetrahedrite Cu12Sb4S13 bulk material by spark plasma sintering. High purity Cu12Sb4S13 can be quickly obtained by two sintering procedures at temperatures from the range of 420 °C to 440 °C for 1 h. Appropriate reduction of Cu content (Cu12+xSb4S13, x ⩽ –0.05) or CuS content (Cu12−ySb4S13−y, y = 0.1 or 0.3) was beneficial to fabricate Cu12Sb4S13. The secondary resintering improved the purity of Cu12Sb4S13 material. The first-order magnetic phase transformation with magnetic hysteresis effect was confirmed by the behavior of susceptibility, heat capacity and resistivity. The magnetization showed a linear increase with increasing field (up to 7 T) and non-saturation behavior was observed. The impurities in stibnite mineral Sb2S3 had a weak influence on the transformation temperature but affected the low-temperature magnetization value (~0.15, close to natural tetrahedrite). Similar transformation was observed by the analysis of heat capacity. The properties such as electrical resistivity, Seebeck coefficient and thermal conductivity were also measured for Cu11.9Sb4S13 and Cu11.9Sb4S12.9. The maximum figure of merit ZT of Cu11.9Sb4S12.9 was 0.22 at 367 K.

15

Single sheet tester for measuring core losses with novel adaptive algorithm of waveform

88%

Lerch T. , Rad M. , Rams W.

Archives of Electrical Engineering

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2022

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tom Vol. 71, nr 4

851--864

EN

This paper presents a novel method of waveform generation in a single-sheet tester (SST) for measuring core losses and permeability in a steel sheet. Some improvements and modifications of the apparatus are also described. The improved way of working of a SST is important, especially in the extended range of polarization (up to 1.9 T). The system consists of hardware and software. Everything together was tested and has given good results. The proposed algorithm is described and compared to previously known methods.

16

Magnetic studies of 0.7(Fe2O3)/0.3(ZnO) nanocomposites in nanopowder form and dispersed in polymer matrix

88%

Typek J. , Wardal K. , Zolnierkiewicz G. , Szymczyk A. , Guskos N. , Narkiewicz U. , Piesowicz E.

Materials Science Poland

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2016

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tom Vol. 34, No. 2

286--296

EN

Magnetic properties of 0.7(Fe2O3)/0.3(ZnO) nanocomposite synthesized by traditional wet chemistry method and containing only two phases: ZnO (nonmagnetic) and Zn Fe2O4 (magnetic, with nanocrystallites of average size 12 nm, but forming large agglomerates, up to 100 nm in size) were studied by DC magnetization and ferromagnetic resonance (FMR). The investigated nanocomposite was either in a form of nanopowder or dispersed at concentration of 0.1 wt.% in poly(ethylene naphthalate-block-tetramethylene oxide) PTMO-b-PEN polymer matrix. Similarities and differences in magnetic behavior of these two samples revealed by the study of static magnetization and FMR spectra have been discussed relative to different morphologies and the associated variation of interparticle interactions. Moreover, thermal and thermo-oxidative stability of the nanocomposite and the neat polymer have been studied by thermogravimetric method.

17

Magnetic properties of the mixed spin-5/2 and spin-3/2 Blume-Capel Ising system on the two-fold Cayley tree

88%

Yessoufou R. , Amoussa S. , Hontinfinde F.

Open Physics

|

2009

|

tom 7

|

nr 3

555-567

EN

We use exact recursion relations to study the magnetic properties of the half-integer mixed spin-5/2 and spin-3/2 Blume-Capel Ising ferromagnetic system on the two-fold Cayley tree that consists of two sublattices A and B. Two positive crystal-field interactions Δ1 and Δ2 are considered for the sublattice with spin-5/2 and spin-3/2 respectively. For different coordination numbers q of the Cayley tree sites, the phase diagrams of the model are presented with a special emphasis on the case q = 3, since other values of q reproduce similar results. First, the T = 0 phase diagram is illustrated in the (D A = Δ1/J,D B = Δ2/J) plane of reduced crystal-field interactions. This diagram shows triple points and coexistence lines between thermodynamically stable phases. Secondly, the thermal variation of the magnetization belonging to each sublattice for some coordination numbers q are investigated as well as the Helmoltz free energy of the system. First-order and second-order phase transitions are found. The second-order phase transitions become sharper and sharper when D A or D B increases. The first-order transitions only exist for some appropriate non-zero values of D A and/or D B. The corresponding transition lines never connect to the second-order transition lines. Thus, the non-existence of tricritical points remains one of the key features of the present model. The magnetic exponent β 0 of the model is estimated and found to be ¼ at small values of D A = D B = D and β 0 = ½ at large values of D. At intermediate values of D, there is a crossover region where the magnetic exponent displays interesting behaviours.

18

Magnetostrictive Functional Materials of Tb0.27Dy0.73(Fe1-xAlx)2 Series as Prospective Constituents of Magnetoelectric Composites

88%

Winiarska B. , Guzdek P. , Kuciakowski J. , Tokarz W. , Sikora M. , Pszczoła J.

Archives of Metallurgy and Materials

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2023

|

tom Vol. 68, iss. 1

215--222

EN

Structural, magnetic, and magnetostrictive properties of two-sublattice Tb0.27Dy0.73(Fe1-xAlx)2 polycrystalline intermetallic ferrimagnets (x = 0-0.2 and 1.0) were studied using X-ray powder diffraction, magnetometry, and strain gauge magnetostriction measurements. Temperature dependences of magnetization starting from 80 K were presented, and Curie temperatures were estimated. Coercive force, residual, and saturation magnetizations were determined from the magnetic hysteresis loops at room temperature. Longitudinal, transversal, form and volume magnetostrictions were investigated against the x parameter and the intensity of the magnetic field. The piezomagnetic coefficients were determined and the maximum value at the field below 1 kOe, even enhanced than that in Terfenol-D, was observed for the material TTb0.27Dy0.73(Fe0.9Al0.1)2. It means that this compound is promising for use in magnetoelectric composites.

19

Square Ising Nanowire on the Bethe Lattice

88%

Albayrak E.

Acta Physica Polonica A

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2017

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tom 131

|

nr 6

1470-1473

EN

The square-type nanowire is simulated on the Bethe lattice by using the core-shell structure consisting of the Ising spins. A nanoparticle is formed by placing a spin to the center and four others to the corners of a square. Then, each nanoparticle is combined with two neighboring ones with a perfect alignment of the squares to form the nanowire. Only nearest-neighbor spin interactions, either ferromagnetic or antiferromagnetic type, are allowed. The phase diagrams are calculated by studying the thermal variations of magnetizations for various values of bilinear interactions. It is found that the model gives both second- and first-order phase transitions in addition to the tricritical points and compensation temperatures.

20

Magnetic and electric behavior of NiFe2O4-PVDF nanocomposites

88%

Sen S. , Panda A. K. , Prasad K.

Materials Science Poland

|

2012

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tom Vol. 30, No. 4

419--425

EN

NiFe2O4-PVDF composites in different ratios (10 %, 30 % and 50 %) were prepared in two steps. Firstly, fine nanosized NiFe2O4 powder was synthesized using the precursor solution method. Then the composites were made by hot-press technique. The presence of both the phases (ceramic and polymer) was confirmed by XRD micrographs. The average particle size of the composites varied from 18-23 nm. SEM micrographs showed that the ferrite particles were embedded in the polymer matrix. The saturation magnetization and the remanence showed an increasing trend with the increase in ferrite content while the coercivity remained almost constant. Impedance plot showed the presence of a single semicircle, which indicates the presence of bulk effect. The composites exhibited non-Debye relaxation. The bulk conductivity followed the Arrhenius type of behavior. The conduction mechanism was explained by the Vervey-de-Boer mechanism.