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Mechanic, Half-Metallic and Thermoelectric Properties of the PdZrTiAl under pressure: A DFT study

Parsamehr S., Boochani A., Sartipi E., Amiri M., Solaymani S., Naderi S., Aminian A.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 1

459--470

EN

The half-metallic, mechanical, and transport properties of the quaternary Heusler compound of PdZrTiAl is discussed under hydrostatic pressures in the range of –11.4 GPa to 18.4 GPa in the framework of the density functional theory (DFT) and Boltzmann quasi-classical theory using the generalization gradient approximation (GGA). By applying the stress, the band gap in the minor spin increases so that the lowest band is obtained 0.25 eV at the pressure of –11.4 GPa while the maximum gap is calculated 0.9 eV at the pressure of 18.4 GPa. In all positive and negative pressures, the PdZrTiAl composition exhibits a half-metallic behavior 100% spin polarization at the Fermi level. It is also found that applying stress increases the Seebeck coefficient in both spin directions. In the minority spin, the n-type PdZrTiAl, the power factor (PF) for all the cases is greater in the equilibrium state than the strain and stress conditions whereas in the majority spin, the PF value of the stress state is greater than the other two. The non-dimensional figure of merit (ZT) is significant and is about one in spin down in the room temperature for the all pressure states that it remains on this value by applying pressure. The obtained elastic constants indicate that the PdZrTiAl crystalline structure has a mechanical stability. Based on the Yong (E), Bulk (B) and shear (G) modulus and Poisson (n) ratio, the brittle-ductile behavior of this compound has been investigated under pressure. The results indicate that PdZrTiAl has a ductile nature and it is a stiffness compound in which elastic and mechanical instability increases by applying strain.

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First principle calculations of zinc blende superlattice surfaces and multilayers with ferromagnetic dopants

Wronka A.

Materials Science Poland

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2007

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Vol. 25, No. 2

527--532

EN

In order to understand conditions for appearance of half-metallicity in MnAs/AsGa(001) digital alloy superlattices, we calculated the electronic and magnetic structure of zinc blende multilayers in various ab initio supercell geometries for ferromagnetic dopants (Fe, Cr). The bulk atomic structure model is extended allowing consideration of the surface ferromagnetic metal monolayer (Fe, Cr) in the slab approximation. The calculations were performed using the density functional theory (DFT) method within the full-potential and linearized augmented plane-wave (LAPW) approach. This work presents detailed information about total and atom projected density of states (DOS) functions in the surface region of the investigated systems. Our interest was to look for common trends and differences in the electronic structures for different locations of ferromagnetic adatoms and surface monolayer (Fe, Cr) in the zinc blende digital alloy surfaces and multilayers.

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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.