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Total and atomic magnetic moments of Sc 2 VGe as a function of lattice constant with XA and L2 1 atomic competition.
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The site-preference rule (SPR), which is widely used to design and study the properties of full-Heusler alloys X2YZ, is applied to determine the positions of different transition-metal elements with various numbers of valence electrons in Heusler alloys. The scandium-based full Heusler alloys should form an XA structure according to the SPR, becaus...
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... An important role in the rapid growth of this research field was played by the first-principles electronic band structure calculations. On one hand, they successfully explained the origin of half-metallicity and linked it to the magnetic properties through the so-called Slater-Pauling rules [13][14][15][16][17][18], and on the other hand, extended databases built using such calculations resulted in the prediction of hundreds of new Heusler compounds which were later grown experimentally [19][20][21][22][23][24][25][26]. ...
Half-Heusler compounds with 18 valence electrons per unit cell are well-known non-magnetic semiconductors. Employing first-principles electronic band structure calculations, we study the interface properties of the half-Heusler heterojunctions based on FeVSb, CoTiSb, CoVSn, and NiTiSn compounds, which belong to this category of materials. Our results show that several of these heterojunction interfaces become not only metallic but also magnetic. The emergence of spin-polarization is accompanied by the formation of two-dimensional electron gas (2DEG) or hole gas (2DHG) at the interface. We qualitatively discuss the origin of the spin polarization at the interfaces on the basis of the Stoner model. For the cases of magnetic interfaces where half-metallicity is also present, we propose a modified Slater-Pauling rule similar to the one for bulk half-metallic half-Heusler compounds. Additionally, we calculate exchange parameters, Curie temperatures and magnetic anisotropy energies for magnetic interfaces. Our study, combined with the recent experimental evidence for the presence of 2DEG at CoTiSb/NiTiSn heterojunctions might motivate future efforts and studies toward the experimental realization of devices using the proposed heterojunctions.
... Heusler alloys with the mentioned properties are of great interest in the broad range of applications e.g. spin injectors, spin valve, spin torque based random access memories, spintronics, magnetic tunnel junctions, light emitting diodes, optoelectronics and many more [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. It is seen in the recent years that there is a strong demand of clean energy due to large power crisis. ...
The electronic structure, mechanical stability, phonon dispersion and vibrational characteristics of half-Heusler alloys, ScAuX (X = Si, Ge, Sn, Pb) have been analyzed in framework of Density Functional theory(DFT). The alloys are crystallize in face centered cubic having F4¯3m(#216) space group. First-principles simulation reveals that all the alloys are narrow band gap semiconductors. The electronic structure is investigated using generalized gradient approximation under Perdew-Burke-Ernzerhof parameterization(GGA + PBE). To predict the accurate band gap of the compounds, comparatively more refined hybrid functional such as Heyd-Scuseria-Ernzerhof (HSE06) has been taken into account. The calculated elastic constants verify the mechanical stability of all the systems by tolerating Born-Huang criteria. In addition, the phonon dispersion and shear constant also favor in mechanical stability. A detailed investigation of vibrational characteristics have been performed. On the basis of electronic band structure topology and calculated theoretical limit of minimum lattice thermal conductivity, our simulated results predict that all the alloys are promising candidates for thermoelectric applications.
... Extensive investigations on Heusler compounds in this regard has paid rich dividends, as quite a few half-metals and SGSs have been discovered with composition X 2 YZ where X and Y are elements from the 3d series of the periodic table [13][14][15][16][17][18][19]. There are fewer investigations into compounds with either/both X and Y as elements with 4d electrons or one of them being a 4d element [20][21][22]. The presence of both 3d and 4d magnetic elements in the same compound with a Heusler structure is expected to provide interesting perspectives. ...
Employing ab initio electronic structure calculations, we extensively study ternary Heusler compounds with the chemical formula X2X′Z, where X = Mn, Fe or Co; Z = Al or Si; and X′ changes along the row of 4d transition metals. A comprehensive overview of these compounds, addressing the trends in structural, electronic, magnetic properties and Curie temperature, is presented here along with the search for new materials for spintronics applications. A simple picture of hybridization of the d-orbitals of the neighboring atoms is used to explain the origin of the half-metallic gap in these compounds. We show that arrangements of the magnetic atoms in different Heusler lattices are largely responsible for the interatomic exchange interactions that are correlated with the features in their electronic structures as well as the possibility of half-metallicity. We find seven half-metallic magnets with 100% spin polarization. We identify a few other compounds with high spin polarization as ‘near half-metals’ which could be of potential use in applications as well. We find that the major features in the electronic structures remain intact if a 3d X′ constituent is replaced with an isoelectronic 4d, implying that the total number of valence electrons can be used as a predictor of half-metallic nature in compounds from the Heusler family.
... In order to demonstrate their usage as multipurpose materials in various applications, many theoretical and experimental studies on Heusler alloys have been conducted [13][14][15][16][17][18][19][20][21][22][23][24][25][26]. However, there are few experimental and theoretical studies about Ir-based Heusler alloys [27][28][29][30][31][32][33][34]. ...
The magnetic, electronic, elastic and vibrational properties of Ir2MnAl Heusler alloy are investigated with generalised gradient approximation (GGA) within the frame of Density Functional Theory (DFT). The ferromagnetic (FM) and non-magnetic (NM) states of Ir2MnAl Heusler alloy in Cu2MnAl and Hg2CuTi crystal structures have been compared. It is found that the ferromagnetic state in the Cu2MnAl structure is energetically more stable than other states. The obtained structural parameters are consistent with the current experimental and theoretical results. The spin-polarised electronic band structures of the material exhibit half-metallic behaviour with band gap in spin minority state from 0.382 eV at the Γ-X symmetry points, making it useful for spintronics applications. The calculated total magnetic moment of Ir2MnAl Heusler alloy is 4 μB which comply with the Slater-
Pauling rule. Furthermore, the uniform strain has also been implemented to examine the magnetoelectronic and half-metallic properties of this alloy. As a result, the half-metallicity is preserved in
lattice constants between 5.872 Åand 6.187 Å. The obtained negative formation energy indicates both energetic and thermodynamic stability of this alloy. Moreover, the computed elastic constants state
that this material is mechanically stable since it fulfills the Born stability criteria. The calculated B/G ratio and Cauchy pressure imply that Ir2MnAl is a ductile material in nature. Additionally, the vibrational properties are studied and it is found that this material is dynamically stable since there is no negative frequency value in phonon dispersion curves.
... However, only a few publications have been focused on the study of the effect of structural transformations in HA on their optical properties and hence the electronic structure. Han et al have shown significant influence of the alloy symmetry on the electronic structure and magnetic characteristics of the Sc-based HA with XA and L2 1 types of structure [15]. Furthermore, Wan et al have indicated that the calculated IBOC spectra in a Ni 2 MnGa alloy show a noticeable structural dependence [7]. ...
The first-principles calculations of the electronic structures and the interband optical conductivity (OC) spectra have been performed for the stoichiometric Fe2MnGa alloy with L21 and L12 types of atomic ordering. The calculated optical properties of Fe2MnGa alloy for the L21 and L12 phases are complemented by the experimental OC spectra for bulk and thin film Fe-Mn-Ga alloy samples near the stoichiometry 2:1:1 with L21 and L12 (for bulks) as well as the body-centered-cubic and face-centered-cubic (for films) structures, respectively. A reasonable agreement between experimental and calculated interband OC spectra was obtained for both phases of the alloy. The experimental data show no significant difference in the OC spectra with respect to the degrees of atomic and magnetic orders of the samples.
... However, only a few publications have been focused on the study of the effect of structural transformations in HA on their optical properties and hence the electronic structure. Han et al have shown significant influence of the alloy symmetry on the electronic structure and magnetic characteristics of the Sc-based HA with XA and L2 1 types of structure [15]. Furthermore, Wan et al have indicated that the calculated IBOC spectra in a Ni 2 MnGa alloy show a noticeable structural dependence [7]. ...
The first-principles calculations of the electronic structures and the interband optical conductivity (OC) spectra have been performed for the stoichiometric Fe$_{2}$MnGa alloy with L2$_{1}$ and L1$_{2}$ types of atomic ordering. The calculated optical properties of Fe$_{2}$MnGa alloy for the L2$_{1}$ and L1$_{2}$ phases are complemented by the experimental OC spectra for bulk and thin film Fe-Mn-Ga alloy samples near the stoichiometry 2:1:1 with L2$_{1}$ and L1$_{2}$ (for bulks) as well as the body-centered-cubic and face-centered-cubic (for films) structures, respectively. A reasonable agreement between experimental and calculated interband OC spectra was obtained for both phases of the alloy. The experimental data show no significant difference in the OC spectra with respect to the degrees of atomic and magnetic orders of the samples.
The first-principles calculations have been employed to explore structural, electronic, magnetooptical and thermodynamic properties of Half-Heusler compounds XNiSb (X = Er, Ho, Yb). The FP-LAPW technique is executed using the WIEN2K package to simulate stable electronic, structural, magnetooptical and thermodynamics properties of studied half-Heusler compounds. The electronic properties (DOS and energy band structures) have been elucidated, considering the strong correlation between the d/f-states of Ni/X-atoms. It is evident from the presented GGA and GGA + U results that XNiSb (X = Er, Ho, Yb) show metallic nature; however, mBJ + U results show that these compounds are intermetallic. The \({\varepsilon }_{2}(\omega )\) spectra reveal that XNiSb (X = Er, Ho, Yb) absorb a significant number of incident photons over a broad spectrum (∼1.0 to ∼6.0 eV). These compounds are weak reflectors of incident photons and reflect ∼40% of incident photons on the entire energy range. ErNiSb/HoNiSb show significant values of magnetic moments due to the splitting of [\({4f}^{12}]\)/[\({4f}^{11}]\) localized orbitals and are promising candidates for prospective spintronic applications. The elucidated thermodynamic characteristics reveal that these compounds are thermally stable.
Half-Heusler compounds with 18 valence electrons per unit cell are well-known nonmagnetic semiconductors. Employing first-principles electronic band-structure calculations, we study the interface properties of the half-Heusler heterojunctions based on FeVSb, CoTiSb, CoVSn, and NiTiSn compounds, which belong to this
category of materials. Our results show that several of these heterojunction interfaces become not only metallic but also magnetic. The emergence of spin-polarization is accompanied by the formation of two-dimensional electron gas or hole gas at the interface. A qualitative analysis of the origin of the spin polarization at the
interfaces suggests that strong correlations are responsible. For the cases of magnetic interfaces where half-metallicity is also present, we propose a modified Slater-Pauling rule similar to the one for bulk half-metallic half-Heusler compounds. Additionally, we calculate exchange parameters, Curie temperatures, and magnetic
anisotropy energies for magnetic interfaces. Our study, along with recent experimental evidence confirming the presence of two-dimensional electron gas at CoTiSb/NiTiSn heterojunctions, may motivate future efforts to explore and realize device applications using these heterojunctions.
Citation: Al-Masri, K.M.; Abu-Jafar, M.S.; Farout, M.; Dahliah, D.; Mousa, A.A.; Azar, S.M.; Khenata, R. Structural, Elastic, Electronic, and Magnetic Properties of Full-Heusler Alloys Sc 2 TiAl and Sc 2 TiSi Using the FP-LAPW Method. Magnetochemistry 2023, 9, 108. https://doi.org/ 10.3390/magnetochemistry9040108 Academic Editors: Devashibhai Adroja and Dmitry Alexandrovich Filippov Abstract: In this article, the structural, elastic, electronic, and magnetic characteristics of both regular and inverse Heusler alloys, Sc 2 TiAl and Sc 2 TiSi, were investigated using a full-potential, linearized augmented plane-wave (FP-LAPW) method, within the density functional theory. The optimized structural parameters were determined from the minimization of the total energy versus the volume of the unit cell. The band structure and DOS calculations were performed within the generalized gradient approximation (GGA) and modified Becke-Johnson approaches (mBJ-GGA), employed in the Wien2K code. The density of states (DOS) and band structure (BS) indicate the metallic nature of the regular structure of the two compounds. The total spin magnetic moments for the two compounds were consistent with the previous theoretical results. We calculated the elastic properties: bulk moduli, B, Poisson's ratio, ν, shear modulus, S, Young's modulus (Y), and the B/s ratio. Additionally, we used Blackman's diagram and Every's diagram to compare the elastic properties of the studied compounds, whereas Pugh's and Poisson's ratios were used in the analysis of the relationship between interatomic bonding type and physical properties. Mechanically, we found that the regular and inverse full-Heusler compounds Sc 2 TiAl and Sc 2 TiSi were stable. The results agree with previous studies, providing a road map for possible uses in electronic devices.
