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X-ray photoelectron spectroscopy (XPS) study of Heusler alloy (Co2FeAl) interfaced with semiconductor (n-Si) structure

Kumar Arvind, Srivastava P. C.

Materials Science Poland

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2019

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Vol. 37, No. 1

116--121

EN

Layered magnetic heterostructures are very promising candidates in spintronics in which the influences of interfaces, surfaces and defects play a crucial role. X-ray photoelectron spectroscopy (XPS) study has been performed for studying in detail the chemical state and electronic structure of Co2FeAl (CFA) Heusler alloy interfaced with Si substrates. XPS survey scan spectra have clearly shown the presence of Fe, Co and Al signal along with the signal due to Si. The presence of Co, Fe and Al signal confirms the formation of CFA alloy phase. Our XPS results support our previous study [1] on CFA/Si structure in determining the magnetic and transport properties across the interface.

2

Site preference and electronic structure of Mn2RhZ (Z = Al, Ga, In, Si, Ge, Sn, Sb): a theoretical study

Ren Z., Liu Y., Li S., Zhang X., Liu H.

Materials Science Poland

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2016

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Vol. 34, No. 2

251--259

EN

The electronic structure and magnetism of Mn₂RhZ (Z = Al, Ga, In, Si, Ge, Sn, Sb) Heusler alloys have been studied by using first-principles calculations. Three half-metallic ferromagnets, namely, Mn₂RhAl, Mn₂RhGe and Mn₂RhSb have been considered. The calculated equilibrium lattice constant increases with increasing atomic number of Z atoms lying in same column of periodic table. The calculated total magnetic moments M are 2 μ_B/f.u. for Mn₂RhAl and Mn₂RhGa, 3 μ_B/f.u. for Mn₂RhSi, Mn₂RhGe and Mn₂RhSn, and 4 μ_B/f.u. for Mn₂RhSb, which agrees with the Slater-Pauling curve quite well. In all these compounds, except for Mn₂RhSb, the moments of Mn (A) and Mn (B) are antiparallel to each other. The total magnetic moments of the three considered half-metals assume integral values in a wide range of equilibrium lattice parameters.

3

Magnetic transformation in Ni-Mn-In Heusler alloy

Kuzma M., Maziarz W, Stefaniuk I.

Nukleonika

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2015

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Vol. 60, No. 3, part 1

435--438

EN

Magnetic properties of a Ni50Mn35.5In14.5 Heusler ribbon were studied by ferromagnetic resonance (FMR) in the temperature range of 335–100 K. In the temperature region of 265–170 K, the FMR signal disappeared, in spite of the fact that this region comprised the main crystal transformation temperatures: Ms, Mf, As, Af. In the austenite crystal state, a weak antiferromagnetic interaction was observed, whereas ferromagnetism was detected in the low temperature martensitic state.

4

Synthesis and characterization of Co2FeAl Heusler alloy nanoparticles

Kumar A., Srivastava P. C.

Materials Science Poland

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2013

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Vol. 31, No. 4

501--505

EN

Heusler alloy Co2FeAl (CFA) nanoparticles have been synthesized by reducing a mixture of the precursors: CoCl2_6H2O, Fe(NO3)3_9H2O and AlCl3_6H2O under H2 atmosphere. XRD, SEM and TEM techniques have been used for the characterization of the prepared material. XRD and SAED data from TEM show the formation of mixed phases of L21, B2 and A2 type crystal structure of the alloy. The estimated particle size from XRD data and TEM micrograph has been found in the range of 10 nm to 50 nm. The saturation magnetization has been found of 115 emu/g from M-H characteristics which is close to its bulk value of saturation magnetization. Chemical composition of the elements has also been estimated from EDAX, which shows a ratio of Co:Fe:Al as 2.12:1.06:0.81.

5

Recent progress on Co-base alloys - phase diagrams and application

Ishida K.

Archives of Metallurgy and Materials

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2008

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Vol. 53, iss. 4

1075-1088

EN

This paper presents recent progress on the phase diagrams and design for Co-base alloys, focusing on magnetic recording media, ferromagnetic Co-Ni-Al-base shape memory alloys, half-metallic Heusler alloys and Co-base superalloys. The calcu-lated miscibility gap between ferromagnetic and paramagnetic states in the Co-X(X: Cr, Mo, W) systems has been found to agree well with the experimental results, strongly implying that the magnetic induced phase separation is responsible for the compositional heterogeneity in Co-base magnetic recording media. New ferromagnetic Co-Ni-Al shape memory alloys have also been developed based on phase diagrams, where the introduction of γ(Al structure) to theΒ(B2) matrix was found to drastically improve the ductility. The phase stability of half-metal Heusler Co-Cr base alloys is discussed in relation to the order-disorder transition, Curie temperaturę and the spin polarization ratio. Finally, the possibility of potent strengthening of Co-base superalloys by precipitation of the γ'(Ll2) phase is presented.

PL

Praca przedstawia przegląd aktualnych badań nad wykresami fazowymi i projektowaniem stopów na osnowie kobaltu z ukierunkowaniem na środki magnetycznego przekazu, ferromagnetyczne stopy Co-Ni-Al-osnowie z pamięcią kształtu, pół-metaliczne stopy typu Heusler'a i superstopy na osnowie kobaltu. Wykazano, że obliczone zakresy rozwarstwienia pomiędzy stanam i ferromagnetycznymi i paramagnetycznymi w układach Co-X (X = Cr, Mo, W) zgadzają się z wynikami doświadczalnymi, wyraźnie wskazując na to, że wzbudzone magnetycznie rozdzielenie fazowe jest odpowiedzialne za złożoną niejednorodność w stopach na osnowie kobaltu z ukierunkowaniem na środki magnetycznego przekazu. Nowe ferromagnetyczne stopy Co-Ni-Al. z pamięcią kształtu zostały opracowane w oparciu o wykresy fazowe, także w przypadkach kiedy wprowadzenie γ(Al. struktury) do Β(B2) osnowy powodowało drastyczny wzrost plastyczności. Stabilność fazowa pół-metalicznych stopów Heusler'a na osnowie Co-Cr jest dyskutowana w aspekcie przejścia porządek-nieporządek, temperatury Curie i jeżeli chodzi o stosunek spinowej polaryzacji. W efekcie końcowym, przedstawiona jest możliwość potencjalnego umocnienia superstopów na osnowie kobaltu drogą wydzielania fazy γ'(Ll2).

6

Structure and magnetism of Co2CrAl Heusler alloy films

Dubowik J., Gościańska I., Kudryavtsev Y. V., Oksenenko V. A.

Materials Science Poland

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2007

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Vol. 25, No. 4

1281--1287

EN

We report on magnetic properties of Co2CrAl thin films. Low-field magnetization measurements show that the films with the best B2/L21 structure exhibit ferromagnetic order below the Curie temperature TC ??330-340 K and below 200 K they exhibit magnetic characteristics suggesting the presence of antiferromagnetic ordering. Our ferromagnetic resonance measurements confirm a complex magnetic phase diagram of Co2CrAl due to a disorder between Co and Cr sites in nominally L21 or B2 structures.

7

Role of the magnetic impurities in Ni2Ti1-xMnxSn Heusler type alloys. Ab-initio calculations

Jezierski A., Kowalewski P., Dubowik J.

Materials Science Poland

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2007

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Vol. 25, No. 2

553--557

EN

We have studied electronic and magnetic properties of Ni2Ti1-xMnxSn Heusler type alloys. The calculations were carried out within the density functional theory using ab-initio TB LMTO-ASA method. We found that Ni2Ti1-xMnxSn becomes magnetic for a small manganese concentration x = 0.0625.

8

Films of Heusler alloys

Dubowik J., Gościańska I., Szlaferek A., Kudryavtsev Y. V.

Materials Science Poland

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2007

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Vol. 25, No. 2

583--598

EN

Heusler alloys (HA) are a class of materials which may be metals, semiconductors or semimetals, most of them being ferromagnets. Some new applications of HA in spintronics and micro-electromagnetic actuators require their preparation in the form of thin films. Deposition of a HA film is a challenging task from the point of view of its proper ordering. Local disorder and antisite disorder are the most probable reasons of failure in achieving 100% polarization in nanostructures containing HA layers. We will review some examples of tunnel magnetoresistance structures that include Co2YZ HA layers (Y = Mn, Cr, Fe, Z = Al, Si, Ga). The influence of structural ordering on the magnetic and transport properties of Co2MnGa films are given with an emphasis on crystallization process of the films with amorphous structure and a further improvement of its structural ordering. Equally difficult task concerns preparation of HA films with shape memory (SM) effect. Recent achievements in technology of HA with SM will be reviewed. We will focus on non-stoichiometric Ni-Mn-Ga sputtered films. Their SM properties critically depend on composition and post-deposition annealing conditions. By a proper choice of these conditions, the ordered Ni-Mn-Ga films exhibit a well defined SM effect near room temperature.