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1

The Structure and Magnetocaloric Effect of MnCoGe Alloy Modified by Nb

Kutynia Karolina, Gębara Piotr, Przybył Anna

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 3

879--883

EN

The aim of this work was to investigate the effect of partial substitution of Mn by Nb on structure and thermomagnetic properties in the (Mn, Nb)-Co-Ge alloy. The master alloys were prepared by arc-melting in an arc furnace with high purity of constituent elements under a low pressure of Ar. The prepared specimens were studied in as-cast state. The X-ray was performed by BRUKER D8 Advance diffractrometer with Cu Kα radiation. The analysis of the XRD pattern revealed coexistence of two orthorhombic phases with different lattice constants. The analysis of the temperature dependence of magnetizaton confirmed the XRD results and showed that produced material manifested two magnetic phase transitions corresponding to detected phases. The values of the Curie temperature were 275 and 325 K. The values of magnetic entropy change ∆SM equaled 3.30 and 2.13 J/(kg K), respectively for recognized phases. Biphase structure of produced material allowed to reach relatively high refigeration capacity 307 J/(kg). Moreover, the analysis of field dependences of magnetic entropy change (∆SM = CBn) allowed to construct temperature dependence of exponent n. The analysis of elaborated n vs. T curve confirmed biphasic structure of produced material.

2

The Magnetic Entropy Changes in Pb Doped Ni-Mn-Cu-Ga Alloys

Sielicki K., Zygmuntowicz J., Wróblewski R., Leonowicz M.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 2

823--825

EN

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.

3

Structural stability, electronic structure and magnetic properties of the new hypothetical half-metallic ferromagnetic full-Heusler alloy CoNiMnSi

Elahmar M. H., Rached H., Rached D., Benalia S., Khenata R., Biskri Z. E., Bin Omran S.

Materials Science Poland

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2016

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Vol. 34, No. 1

85--93

EN

We investigated the structural stability as well as the mechanical, electronic and magnetic properties of the Full-Heusler alloy CoNiMnSi using the full-potential linearized augmented plane wave (FP-LAPW) method. Two generalized gradient approximations (GGA and GGA + U) were used to treat the exchange-correlation energy functional. The ground state properties of CoNiMnSi including the lattice parameter and bulk modulus were calculated. The elastic constants (C-ij) and their related elastic moduli as well as the thermodynamic properties for CoNiMnSi have been calculated for the first time. The existence of half-metallic ferromagnetism (HM-FM) in this material is apparent from its band structure. Our results classify CoNiMnSi as a new HM-FM material with high spin polarization suitable for spintronic applications.

4

Determination of Ressidual Pseudo-Chemical Energy and Energy Dissipative During Reversible Martensitic Transformation in Ni52,2Mn21,3Ga26,5 Alloy

Bramowicz M.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2011

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nr 14(2)

279-285

EN

In this paper we present results of an analysis of the influence of annealing time on the residual pseudo-chemical energy and dissipative energy Fdis(z) during reversible martensitic transformation. Analysis was performed without equilibrium temperature and basis on the model proposed in the study: (LIKHACHEV 1998). From designated courses of residual non-chemical and pseudo-chemical dissipative energies come, that carried thermal treatment causes significant changes of them. Immediately after casting the studied alloy shows continuous increase of the dissipative energy with increasing of martensite fraction. After annealing at the time from 1-0 h, curves Fdis(z) have a curse close to constant function whereas beyond this range show dynamic increasing or decreasing of dissipation energy.

PL

W pracy przedstawiono wyniki przeprowadzonej analizy wpływu czasu wygrzewania próbek stopu Ni52,2Mn21,3Ga26,5 na resztkową energię sprężystą oraz energię dyssypowaną Fdis(z) podczas odwracalnej przemiany martenzytycznej. Analizę przeprowadzono z pominięciem temperatury równowagi fazowej na podstawie modelu zaproponowanego w pracy LIKHACHEVA (1998). Z wyznaczonych przebiegów zmian resztkowej energii sprężystej oraz energii rozpraszanej wynika, że przeprowadzona obróbka termiczna powoduje znaczne ich zmiany. W stanie bezpośrednio po wytopie badany stop wykazuje ciągły wzrost energii rozpraszanej wraz ze wzrostem zawartości frakcji martenzytu. Po zastosowaniu wygrzewania w czasach 1-20 h, krzywe Fdis(z) mają przebieg zbliżony do funkcji stałej, natomiast poza nim wykazują dynamiczny wzrost bądź spadek energii dyssypowanej.

5

Effect of annealing on the structure and properties of Ni46.4 Mn 28.5 Ga 25.1 single crystal

Wróblewski R., Sielicki K., Leonowicz M.

Inżynieria Materiałowa

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2010

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Vol. 31, nr 3

284-286

EN

Effect of annealing at 1073 K for 12 hours on the structure, transformation temperatures and magneto-mechanical properties of Ni46.4Mn28.5Ga25.1 single crystal was studied. Slow cooling from the temperature above the B2-L21 transformation allows to eliminate phases other than martensitic and to refine the 7M martensite structure. The annealing is also a good method to control structural and magnetic transformation temperatures. Magneto-mechanical properties reveal significant change after the heat treatment. Strain in the magnetic field increases over four times after annealing in comparison to that in the as-cast state.

PL

W pracy opisano wpływ wyżarzania w temperaturze 1073 K przez 12 godzin na strukturę, temperaturę przemian oraz właściwości magneto-mechaniczne monokryształu o składzie opisanym wzorem Ni46,4Mn28,5Ga25,1. Wolne chłodzenie z temperatury powyżej przemiany B2-L21 umożliwia eliminację faz innych niż martenzytyczna oraz wpływa na poprawę struktury martenzytu modulowanego 7M (rys. 2). Obróbka cieplna jest również skuteczną metodą kontroli temperatury przemian strukturalnej i magnetycznej (tab. 1., rys. 1). Właściwości magneto-mechaniczne zmieniają się w sposób znaczący w wyniku obróbki cieplnej. Odkształcenie w polu magnetycznym po wyżarzaniu wzrasta ponad czterokrotnie w porównaniu ze stanem przed wyżarzaniem (rys. 3).

6

Crystallographic and microstructural properties of the Ni2,14 Mn0,86 Ga alloy

Breczko T., Bramowicz M.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2004

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nr 7

191-199

EN

The paper presents the results of experimental investigations into the structure of the Ni2,14Mn0,86Ga alloy immediately after casting. The study was performed using an atomic force microscope (AFM), an optical microscope and an X-ray diffractometer (XRD). The results of microscopic analyses (AFM + OM) indicate that grain structure is non-homogenous. Twin structure was not observed immediately after casting. However, the columnar structure of alloy grains suggests that twin structure can be obtained after heat treatment. During XRD investigations the Ni2,14Mn0,86Ga alloy was exposed to the effects of an external magnetic field whose intensity varied from 130¸250 mT. The results were analyzed assuming an ideal arrangement of atoms in the crystal lattice in the austenitic phase. The crystallographic R factor of structure divergence was determined for particular magnetic intensities.

PL

Praca przedstawia eksperymentalne wyniki badań struktury stopu Ni2,14Mn0,86Ga w stanie bezpośrednio po odlaniu. Badania przeprowadzono na mikroskopie sił atomowych, (AFM), mikroskopie optycznym oraz dyfraktometrze rentgenowskim. Badania przeprowadzone zarówno na mikroskopie sił atomowych, jak i mikroskopie optycznym wskazują na niejednorodną budowę ziarn. W stanie bezpośrednio po odlaniu nie stwierdzono wyraźnej struktury bliźniakowej, ale kolumnowa budowa ziarn umożliwia uzyskanie struktury bliźniakowej z wyraźnymi granicami przez zastosowanie obróbki cieplnej. Podczas badań dyfraktometrycznych stop Ni2,14Mn0,86Ga poddano oddziaływaniu zewnętrznego pola magnetycznego o natężeniu od 130 do 250 mT. Badania przeanalizowano przy założeniu występowania stanu austenitycznego oraz idealnego uporządkowania atomów w sieci krystalicznej. Dla poszczególnych obciążeń magnetycznych wyznaczono wskaźnik R rozbieżności struktury.

7

Mössbauer study of the Heusler-type Fe2MAl compounds for M = V, Cr, Fe, Co, Ni

Popiel E., Zarek W., Tuszyński M.

Nukleonika

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2004

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Vol. 49,suppl.3

49-52

EN

The crystal structure and magnetic properties of Fe2MAl compounds for M = V, Cr, Fe, Co and Ni were investigated by X-ray, magnetostatic and Mössbauer effect methods. It was found that the investigated compounds possess not perfectly ordered fcc structure of the L21-type. With increasing number of 3d electrons of M component the transition from the paramagnetic to ferromagnetic behaviour follows. Mössbauer spectra were analysed by a hyperfine field distribution method. They are characterictic of the ferromagnetic phase for M = Fe, Co and Ni and indicated the early observed preference of these atoms for the Fe sites.