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Wyświetlanie 1-11 z 11
Tytuł:
Struktura elektronowa pasmowa i właściwości ferroelektryczne kryształów grupy TGS
Autorzy:
Andriyevskyy, B.
Patryn, A.
Kurlyak, V.
Romanyuk, M.
Stadnyk, V.
Powiązania:
https://bibliotekanauki.pl/articles/118522.pdf
Data publikacji:
2014
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
kryształy ferroelektryczne
struktura elektronowa pasmowa
temperatura Curie
ferroelectric crystals
electronic band structure
Curie temperature
Opis:
Wykonano porównawcze badania struktur elektronowych pasmowych ferroelektrycznych kryształów siarczanu trójglicyny (TriGlycine Sulfate, TGS), (CH2NH2COOH)3⋅H2SO4, selenianu trójglicyny (TriGlycine Selenate, TGSe), (CH2NH2COOH)3⋅H2SeO4, oraz fluoroberylanu trójglicyny (TriGlycine FluoroBeryllate, TGFB), (CH2NH2COOH)3⋅H2BeF4. Odpowiednie obliczenia z pierwszych zasad (ab initio) przeprowadzono w ramach teorii funkcjonału gęstości z uwzględnieniem międzyatomowych oddziaływań dyspersyjnych. Zastosowana metoda pozwoliła na otrzymanie wyników, lepiej pokrywających się z badaniami doświadczalnymi. Po raz pierwszy została zaobserwowana korelacja obliczonej energii całkowitej i temperatury Curie kryształów TGS, TGSe i TGFB.
Comparative studies of the electronic band structures of the ferroelectric crystals triglycine sulfate (TGS) (CH2NH2COOH)3⋅H2SO4, triglycine selenate (TGSe) (CH2NH2COOH)3⋅H2SeO4 and triglycine fluoroberyllate (TGFB) (CH2NH2COOH)3⋅H2BeF4 have been performed. The respective ab initio calculations have been carried out in the framework of the density functional theory (DFT) with taking into account the interatomic dispersion interactions. The method applied has permitted to obtain results which agree better with corresponding experimental studies. The correlation of the calculated total energy and the Curie temperature for TGS, TGSe and TGFB has been detected for the first time.
Źródło:
Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej; 2014, 6; 5-14
1897-7421
Pojawia się w:
Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Magnetic Entropy Changes in Pb Doped Ni-Mn-Cu-Ga Alloys
Autorzy:
Sielicki, K.
Zygmuntowicz, J.
Wróblewski, R.
Leonowicz, M.
Powiązania:
https://bibliotekanauki.pl/articles/354050.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
magnetocaloric effect
magnetic entropy change
Curie temperature
Heusler alloys
Opis:
Effect of Pb addition on magnetocaloric properties of Ni50 Mn18,75 Cu6,25-aPbaGa25 (a = 1, 2, 3, 4, 5) alloys was investigated experimentally. The magnetic measurements conducted at low field of 4 kA/m showed that addition of Pb led to separation of the both transformation temperatures and significantly shifted the structural transition effect towards lower temperatures as well as increased the Curie temperature. The analysis of isothermal magnetic curves allowed for the calculation of magnetic entropychange (ΔSM). Although the peak values of |ΔSM| for alloys containing 4 and 5 at.% Pb, ~3 J/(kg*K) and ~1.5 J/(kg*K) respectively, are low they stretch over the structural transformation and Curie temperature, and are at least 30 K wide at half maximum height.
Źródło:
Archives of Metallurgy and Materials; 2020, 65, 2; 823-825
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Selected Alloying Elements on the Soft-Magnetic and Mechanical Properties of Injection-Cast Fe61Co10Y8Me1B20 Alloys (Me = Nb, W or Mo)
Autorzy:
Pietrusiewicz, P.
Nabiałek, M.
Powiązania:
https://bibliotekanauki.pl/articles/356969.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
magnetic properties
mechanical properties
abrasion resistance
microhardness
Curie temperature
Opis:
Properties of amorphous alloys differ from each other when they are produced at different cooling rates and from different chemical compositions. This paper presents studies of the magnetic and mechanical properties of Fe61Co10 Y8 Nb1 B20, Fe61 Co10 Y8 -W1 B20 and Fe61 Co10 Y8 Mo1 B20 alloys, in the form of plates, produced by the injection of liquid alloy into a copper mould. Based on the performed studies, it was found that the substitution of 1% non-magnetic additive into the alloy composition had little effect, as regards the values of saturation magnetization (Ms ) and Curie temperature (Tc ). However, in the case of the coercive field, the sample with the W addition had a value almost half that of the other two alloys. For all of the studied alloys, the microhardness was about 1180 μHv100, i.e. significantly higher than for the same materials in the crystalline state.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 1; 61-64
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Preparation, magnetic studies and band structure calculation of NiFe2O4 nanoparticles
Autorzy:
Nabiyouni, G.
Fesharaki, M.
Zolotovsky, A.
Powiązania:
https://bibliotekanauki.pl/articles/1934031.pdf
Data publikacji:
2011
Wydawca:
Politechnika Gdańska
Tematy:
band structure calculation
nickel ferrite nanopowder
Curie temperature
spin-glass
Opis:
We have undertaken a comprehensive theoretical study of the band structure, density of states, dependence of the Curie point and saturation magnetization on the size of NiFe2O4 nanoparticles prepared by the conventional ceramic method. Commercially available NiFe2O4 powder was first annealed in an oxygen environment in a furnace at 1100oC for 3h. The X-ray diffraction pattern indicated that the sample was single-phase at this stage. The average grain size estimated by scanning electron microscopy (SEM) was in the range of 300 to 350nm. The magnetic behavior of the sample at room temperature was studied by means of a superconducting quantum interference device (SQUID). The Curie temperature of the nickel ferrite powder was measured using an LCR meter. The measurement of the Curie temperature and saturation magnetization indicated that a decrease in the grain size leads to a decrease in the Curie temperature and in the saturation magnetization. The small value of saturation magnetization was attributed to a spin-glass-like surface layer on the nanocrystalline nickel ferrite with a ferrimagnetically aligned core (H.Nathani and S.Gubbala 2004 J.Mater. Sci. and Engin. B 111 95). Good agreement was obtained between theory and experimental results.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2011, 15, 1; 107-119
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microstructure and Soft Magnetic Properties of Fe-Zr-(Pt)-Nb-Cu-B Amorphous Alloys
Autorzy:
Gondro, J.
Błoch, K.
Nabiałek, M.
Walters, S.
Powiązania:
https://bibliotekanauki.pl/articles/356965.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
amorphous alloys
Mössbauer spectroscopy
magnetic susceptibility
Curie temperature
magnetic properties
Opis:
This paper presents the results of investigations into the microstructure and magnetic properties of Fe86Zr7Nb1Cu1B5, Fe82Zr7Nb2Cu1B8 and Fe81Pt5Zr7Nb1Cu1B5 alloys. The alloys were investigated in their as-quenched state, in the form of thin ribbons with approximate dimensions as follows: width 3 mm and thickness 20 μm. The investigations were performed utilizing Mössbauer spectrometry and X-ray diffractometry. Also, an evaluation of the low-field magnetic susceptibility and measurements of the magnetization versus temperature and magnetizing field were performed.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 2A; 707-710
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of Co, Ni, and Cr addition on microstructure and magnetic properties of amorphous and nanocrystalline Fe86−xMxZr7Nb2Cu1B4 (M = Co, Ni, CoCr, and Cr, x = 0 or 6) alloys
Autorzy:
Łukiewska, A.
Świerczek, J.
Hasiak, M.
Olszewski, J.
Zbroszczyk, J.
Gębara, P.
Ciurzyńska, W.
Powiązania:
https://bibliotekanauki.pl/articles/147169.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
amorphous materials
nanocrystalline materials
Mössbauer spectroscopy
invar effect
Curie temperature
Opis:
Mössbauer spectra and thermomagnetic curves for the Fe86-xMxZr7Nb2Cu1B4 (M = Co, Ni, CoCr, and Cr, x = 0 or 6) alloys in the as-quenched state and after the accumulative annealing in the temperature range 600–800 K for 10 min are investigated. The parent Fe86Zr7Nb2Cu1B4 amorphous alloy is paramagnetic at room temperature, and substitution of 6 at.% of Fe by Co, Ni, and CoCr changes the magnetic structure – the alloys become ferromagnetic, whereas replacing 6 at.% of Fe with Cr preserves the paramagnetic state. After the heat treatment at 600 K, the decrease of the average hyperfi ne fi eld induction, as compared to the as-quenched state, is observed due to the invar effect. After this annealing, the Curie temperature for all investigated alloys decreases. The accumulative annealing up to 800 K leads to the partial crystallization; α-Fe or α-FeCo grains with diameters in the range of 12–30 nm in the residual amorphous matrix appear.
Źródło:
Nukleonika; 2015, 60, 1; 103-108
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Curie Temperature and Microstructural Changes Due to the Heating Treatment of Magnetic Amorphous Materials
Autorzy:
Gondro, J.
Błoch, K.
Brągiel, P.
Nabiałek, M.
Szota, M.
Powiązania:
https://bibliotekanauki.pl/articles/958228.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
amorphous alloys
magnetic properties
magnetic susceptibility
Mössbauer spectroscopy
Curie temperature
Opis:
Three distinct alloys: Fe86Zr7Nb1Cu1B5, Fe82Zr7Nb2Cu1B8, and Fe81Pt5Zr7Nb1Cu1B5 were characterized both magnetically and structurally. The samples, obtained with spinning roller method as a ribbons 3 mm in width and 20 μm thick, were investigated as-quenched and after each step of a multi steps heating treatment procedure. Each sample was annealed at four steps, fifteen minutes at every temperature, starting from 573K+600K up to +700K depending on type of alloy. Mössbauer spectroscopy data and transmission electron microscope (HRE M) pictures confirmed that the as-quenched samples are fully amorphous. This is not changed after the first stages of treatment heating leads to a reduction of free volumes. The heating treatment has a great influence on the magnetic susceptibilities. The treatment up to 600K improves soft magnetic properties: an χ increase was observed, from about 400 to almost 1000 for the samples of alloys without Pt, and from about 200 to 450 at maximum, for the Fe81Pt5Zr7Nb1Cu1B5. Further heating, at more elevated temperatures, leads to magnetic hardening of the samples. Curie temperatures, established from the location of Hopkinson’s maxima on the χ(T) curve are in very good agreement with those obtained from the data of specific magnetization, σ(T), measured in a field of 0.75T. As a critical parameter β was chosen to be equal 0.36 for these calculations, it confirmed that the alloys may be considered as ferromagnetic of Heisenberg type. Heating treatment resulted in decreasing of TC. These changes are within a range of several K.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 1; 451-456
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hyperfine interaction and some thermomagnetic properties of amorphous and partially crystallized Fe70−xMxMo5Cr4Nb6B15 (M = Co or Ni, x = 0 or 10) alloys
Autorzy:
Rzącki, J.
Świerczek, J.
Hasiak, M.
Olszewski, J.
Zbroszczyk, J.
Ciurzyńska, W.
Powiązania:
https://bibliotekanauki.pl/articles/148195.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Mössbauer spectroscopy
amorphous alloys
magnetic properties
X-ray diffraction
Curie temperature
Opis:
As revealed by Mössbauer spectroscopy, replacement of 10 at.% of iron in the amorphous Fe70Mo5Cr4Nb6B15 alloy by cobalt or nickel has no effect on the magnetic structure in the vicinity of room temperature, although the Curie point moves from 190 K towards ambient one. In the early stages of crystallization, the paramagnetic crystalline Cr12Fe36Mo10 phase appears before α-Fe or α-FeCo are formed, as is confi rmed by X-ray diffractometry and transmission electron microscopy. Creation of the crystalline Cr12Fe36Mo10 phase is accompanied by the amorphous ferromagnetic phase formation at the expense of amorphous paramagnetic one.
Źródło:
Nukleonika; 2015, 60, 1; 121-126
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
EPR study of ZnO:Co thin films grown by the PLD method
Autorzy:
Cieniek, B.
Stefaniuk, I.
Virt, I.
Powiązania:
https://bibliotekanauki.pl/articles/146744.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
electron paramagnetic resonance (EPR)
diluted magnetic semiconductor (DMS)
ZnO:Co
Curie temperature
Opis:
We have studied magnetic properties of zinc-oxide composite doped with a relatively high concentration (4%) of Co ions. Samples were obtained by the pulsed laser deposition (PLD) method with different parameters of the laser ablation. For various samples, the power of laser was changed as well as the temperature of sample heating. Electron paramagnetic resonance (EPR) measurements were carried out and temperature dependence of the EPR spectra was obtained. Analysis of the temperature dependences of the integral intensity of EPR spectra was carried out using the Curie-Weiss law. Fitting yields the following values θCW = 150 K and C = 1.6710, where C is the Curie constant, and θCW is the paramagnetic Curie temperature.
Źródło:
Nukleonika; 2013, 58, 3; 359-363
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Approach to ferromagnetic saturation for amorphous Fe-based alloy
Podejście do ferromagnetycznego nasycenia dla amorficznego stopu na bazie żelaza
Autorzy:
Jeż, B.
Nabiałek, M.
Jeż, K.
Powiązania:
https://bibliotekanauki.pl/articles/182462.pdf
Data publikacji:
2018
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Metalurgii Żelaza im. Stanisława Staszica
Tematy:
massive amorphous materials
approach to ferromagnetic saturation
Curie temperature
X-ray diffraction
Holstein-Primakoff paraprocess
masywny materiał amorficzny
podejście do ferromagnetycznego nasycenia
temperatura Curie
dyfrakcja rentgenowska
paraproces Holsteina-Primakoffa
Opis:
The paper presents the results of research on the structure and selected properties of magnetic alloys based on Fe. The alloy with the chemical composition Fe36Co36Y8B20 was produced using two methods: forcing and sucking the liquid alloy into a copper mould. The alloy was cast in the form of 10 mm × 5 mm × 0.5 mm tiles. The structure of the obtained alloys was examined using X-ray diffraction. The measured diffractograms are typical for amorphous materials. Using the Faraday magnetic balance, the magnetic saturation polarisation curves as a function of temperature were recorded. The Curie temperature of the created alloys, which amounted to approximately 750 K, was determined on the basis of numerical analysis. The original magnetisation curves and static magnetic hysteresis loops were measured using a vibration magnetometer. The produced alloys had a saturation magnetisation of about 1.1T and a coercive field value of about 200 A/m. The curves of primary magnetisation were analysed using H. Kronmüller’s theory. It was found that the magnetising process in the area called the ‘approach to ferromagnetic saturation’ is related to the rotation of the magnetisation vector around the linear defects of the structure.
W pracy zamieszczono wyniki badań struktury i wybranych właściwości magnetycznych stopów na bazie Fe. Stop o składzie chemicznym Fe36Co36Y8B20 wytworzono dwiema metodami: wtłaczania oraz zasysania ciekłego stopu do miedzianej formy. Stop odlewano w postaci płytek o wymiarach 10 mm × 5 mm × 0,5 mm. Strukturę otrzymanych stopów badano przy użyciu dyfrakcji rentgenowskiej. Zmierzone dyfraktogramy są typowe jak dla materiałów amorficznych. Przy użyciu wagi magnetycznej Faraday’a zarejestrowano krzywe magnetycznej polaryzacji nasycenia w funkcji temperatury. Na podstawie analizy numerycznej krzywych wyznaczono temperaturę Curie wytworzonych stopów, która wyniosła około 750 K. Przy użyciu magnetometru wibracyjnego zmierzono pierwotne krzywe magnesowania oraz statyczne pętle histerezy magnetycznej. Wytworzone stopy posiadały magnetyzację nasycenia około 1,1T oraz wartość pola koercji około 200 A/m. Wykorzystując teorię H. Kronmüllera, przeprowadzono analizę krzywych pierwotnego magnesowania. Stwierdzono, że proces magnesowania w obszarze zwanym podejściem do ferromagnetycznego nasycenia związany jest z obrotem wektora magnetyzacji wokół liniowych defektów struktury.
Źródło:
Prace Instytutu Metalurgii Żelaza; 2018, T. 70, nr 3, 3; 40-45
0137-9941
Pojawia się w:
Prace Instytutu Metalurgii Żelaza
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Manganite nanoparticles as promising heat mediators for magnetic hyperthermia: comparison of different chemical substitutions
Autorzy:
Tovstolytkin, A.
Shlapa, Yu.
Solopan, S.
Bodnaruk, A.
Kulyk, M.
Kalita, V.
Zamorskyi, V.
Ryabchenko, S.
Belous, A.
Powiązania:
https://bibliotekanauki.pl/articles/1052905.pdf
Data publikacji:
2018-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
magnetic nanohyperthermia
manganite nanoparticles
complex chemical substitutions
Curie temperature
AC magnetic heating characteristics
Opis:
Magnetostatic properties and AC magnetic heating characteristics of (La,Sr)MnO₃ nanoparticles with substitutions in manganese and lanthanum sublattices have been studied. The nanoparticles with average sizes in the range 25-38 nm were synthesized via sol-gel method. Fe substitution for Mn, as well as Sm substitution for La have been used in the experiment. It is shown that the increase in substitution level (for both Fe and Sm substitutions) results in lowering the Curie temperature T_{C} and weakening heating efficiency under the action of AC magnetic field. The results demonstrate that the action of AC field causes effective heating of nanoparticles at temperatures lower than T_{C}, while heating efficiency becomes strongly reduced at higher temperatures. It is proved experimentally that the substitutions in Mn sublattice result in more rapid changes of magnetic properties, as compared to the substitutions in La one. Thus, complex substitutions based on suitable combinations of substituting elements may serve as an efficient tool to "softly" tune the maximal temperature achieved during the AC magnetic field induced heating of nanoparticles, which is important for application of these materials as heat mediators for self-controlled magnetic nanohyperthermia.
Źródło:
Acta Physica Polonica A; 2018, 133, 4; 1017-1020
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-11 z 11

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