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Heusler alloys based on 4d-elements are relatively less explored though they are known to host interesting electronic/magnetic properties useful for future spintronics applications. Here, we report a comparative study of the structural and magnetic properties of FeRuVSi (FRVS) and FeRuVGe (FRVG) using experimental and theoretical tools. Magneto-transport measurements have also been carried out to probe the role of magnetism on their transport behaviour. Room temperature (T) X-ray diffraction data reveals cubic crystal structure (space group No. 216) with B 2 type antisite disorder between Fe and Ru sites in both the alloys. They show ferromagnetic behaviour below the Curie temperature (T C) 84 K for FeRuVSi and 57 K for FeRuVGe respectively. The field dependence of magnetization at low-T shows saturating (nearly saturating) behaviour for FRVS (FRVG). Transport measurements show metallic behaviour with a sharp reduction in the resistivity near T C. Ab-initio calculations predict nearly half metallic behaviour with ∼ 87 % and ∼ 89 % spin polarization for FRVS and FRVG in their ordered states. The inclusion of antisite disorder changes the magnetic configuration, leading to a visible decrease in the magnetic moment and spin polarization. The calculated net moment and the transport properties agree fairly well with those observed experimentally. These results confirm the importance of disorder in determining the intrinsic properties of these alloys. Such combined studies help in the identification of more novel quantum materials suitable for future spintronic applications. ● We present a comparative study of the magnetic, transport, and electronic properties of FeRuVZ (Z = Si, Ge) Heusler alloys. ● Disorder increases the symmetry of the FeRuVSi Heusler alloy to L 2 1 type, higher than that in FeRuVGe. ● The magnetization goes from saturating to nearly saturating behaviour when Si is changed to Ge. ● High spin polarization and nearly half metallic behaviour in the ordered state in both the alloys. [ABSTRACT FROM AUTHOR]

The double perovskites have outstanding properties for spintronic devices as they are stable, non-toxic, and accomplish the spin polarization. This article studies the function of 5d-electrons of Ta, W, Re and Os to regulate the magnetic properties of Sr 2 CrXO 6. The tolerance factors and formation energies confirm the stability of the structures and the thermodynamics. The half-metallic ferromagnetic nature is found by analyzing the density of states and band structures described by the double exchange model, exchange energy, and exchange constants. According calculations, ferromagnetism is induced by the electron spin due to hybridization process, magnetic moments, exchange energies, and crystal field energy. The thermoelectric applications are further explored by computing and discussing the thermal and electrical conductivities, and Seebeck coefficients. The power factor has also been elaborated for the performance of studied DPs. • Ferromagnetism at high temperature, and spintronic applications. • Spin of electrons operates the devices with multifuctional properties. • Role of 5d electrons and exchange of energies. • Half metallic ferromagnetism and complete spin polarization. • Ultralow low values of thermal conductivity. [ABSTRACT FROM AUTHOR]

We have grown thin films of Co 2 TiSi (CTS) Heusler alloy on n-type Si (100) at different substrate temperatures by electron beam evaporator under a high vacuum. The structural, magnetic, and electric characterizations were carried out and found a strong correlation between the properties and the growth temperatures of the samples. The crystallinity and magnetic moment both were significantly improved with increasing growth temperatures from room temperature to 400 °C. The saturation magnetization of 1.85 µ B at 10 K is close to the theoretical Slater–Pauling value. A large value of spin wave stiffness constant (D = 7.2 meV- nm2) of CTS film manifests the robustness of magnetization. The temperature-dependent longitudinal resistivity demonstrated different scattering phenomenon like weak localization, electron-magnon, electron-election, and electron-phonon interactions. A decrease in residual resistivity (109–49 µΩ-cm) and an increase in residual resistivity ratio (1.2–1.39) indicate an enhancement of crystallinity and structural order of CTS films. By first principle study using DFT calculation we have analyzed the effect of atomic site disorder on electronic properties of both bulk and thin film (220) surface form of CTS Heusler alloy. It has been noticed that the ordered bulk structure shows perfect half-metallic nature but for thin film the spin polarization and moment both are deviated from identical value. The spin polarization and magnetic moment both are reduced a lot by introducing atomic site disorder in L2 1 ordered structure. • Co 2 TiSi films with different subtrate temperatures are grown by electron beam evaporator. • Studies the impact of growth substrate temperatures on structural and magnetic properties Co 2 TiSi film. • Resistivity study suggests the presence of different scattering phenomena. • Effect of atomic site disorder on magnetic moment and spin polarization of bulk and thin film by DFT calculations. [ABSTRACT FROM AUTHOR]

We report a systematic experimental and theoretical study of half-metallic Heusler alloys Mn 2 V 1−x Co x Al (x = 0, 0.25, 0.5, 0.75, 1). In this study, using the arc-melting method and optimizing annealing temperatures, we succeed to synthesize Mn 2 V 1−x Co x Al (x = 0, 0.25, 0.5, 0.75, 1) alloys with evident L2 1 (or XA) order. A near compensated ferrimagnetic moment of 0.02 μB/f.u. at 5 K is observed with the Co concentration of 0.5 which is consistent with the S-P rule. In addition, we systematacially investigate the effects of Co concentration on electronic structure of Heusler alloys Mn 2 V 1−x Co x Al (x = 0, 0.25, 0.5, 0.75, 1) using first-principles calculations, and found that the half-metallic characteristic persists for all Co concentrations. In line with our experimental results, employing appropriate atomic site occupation, we obtained a full compensated ferrimagnetic moment of 0 μB/f.u. for stoichiometric Mn 2 V 0.5 Co 0.5 Al alloy. In addition, the robustness of half-metallic properties for compensated ferrimagnet Mn 2 V 0.5 Co 0.5 Al with the variation of atomic disorder are investigated and the results indicate that the Mn-Al swapping weakly destroys the half-metallic properties and the compensated ferrimagnet Mn 2 V 0.5 Co 0.5 Al alloy maintains the high spin polarization under the effect of B2 disorder. • Mn 2 V 1−x Co x Al (x = 0, 0.25, 0.5, 0.75, 1) alloys with evident L2 1 (or XA) order are fabricated successfully. • Magnetic properties can be regulated by component ratio of Co and V. • A full compensated ferrimagnetic moment of 0 μB/f.u. for stoichiometric Mn 2 V 0.5 Co 0.5 Al alloy is obtained. • Half-metallic properties of Mn 2 V 0.5 Co 0.5 Al is robust against atomic disorder. [ABSTRACT FROM AUTHOR]

The rare earth elements are extensively incorporated in combination with alloys to fill up the demanding gaps of applications in future technologies like thermoelectrics. We give detailed prediction of electronic, magnetic, mechanical, thermoelectric, thermodynamic and optical properties of YCoTiX (X = Al, Ga, Si, Ge) quaternary Heusler alloys. The ground state properties reveal the alloys possess the LiMgPdSn-type structure with F -43 m space group. The spin polarized band structure give us a half-metallic nature at optimized lattice parameters. The minority spin band gaps are found to be indirect with calculated values as 0.53 eV for YCoTiAl, 0.61 eV for YCoTiGa, 0.71 eV and 0.62 eV for YCoTiSi and YCoTiGe, respectively. The total magnetic moment follow the Slater-Pauling curve rule of (M = Z tot – 18). Similarly, the optical properties of these alloys depict the similar behavior of electronic states near the Fermi level with substantially spins oriented along the direction of magnetization in all the alloys. The thermoelectric coefficients are investigated to infer their stand for waste heat recovery systems, where Seebeck coefficients detail their n -type behavior. Conversion efficiency is established using the dimensionless figure of merit, zT calculated as 0.75 at 550 K for YCoTiAl, 0.14 at 750 K for YCoTiGa and 0.31 at 750 K for both YCoTiSi (Ge). Thermodynamic parameters convey that all the alloys possess no anomalies with respect to phase transition or instabilities. • Predicted Heusler alloys are new class of functional materials with perfect half-metallicity. • They present robustness with respect to variation of lattice constant. • They have well established thermoelectric response over high temperature range. • They present good opto-electronic response with far-ultraviolet photo detector applications. • Anisotropic in nature, possibility of micro cracks at growing process. [ABSTRACT FROM AUTHOR]

Bulk (Mn 1- x Co x ) 2 VAl ( x = 0, 0.25, 0.50) alloys in highly ordered L 2 1 structure with a very small amount of B 2 disorder have been prepared and their magnetic properties have been measured. The value of saturation magnetizations of the alloys with x = 0, 0.25 and 0.50 are 1.88 μ B , 0.84 μ B and 0.07 μ B , respectively, being consistent with 2.00 μ B , 1.00 μ B and 0 μ B , respectively, predicted by the Slater–Pauling rule. This indicates that the stoichiometric MnCoVAl alloy is a fully compensated ferrimagnet (FCF). Spin polarization measurements using point contact Andreev reflection technique showed that the quaternary alloys exhibited higher intrinsic spin polarization than the parent ternary composition. The spin polarization of 0.60 deduced for the MnCoVAl alloy suggests that spin-polarized current can be extracted from FCF. Curie temperature ( T C ) and the effective anisotropy constant of (Mn 1- x Co x ) 2 VAl alloys decrease with increase in Co content. [ABSTRACT FROM AUTHOR]

The electronic structure of a ferromagnetic Heusler alloy Co 2 MnSn has been investigated using resonant photoemission spectroscopy to probe the Mn 3 d and Co 3 d states in the valence band region. The motivation of the present work is to understand the low value of spin polarization reported for this system, which mainly depends on the density of states present at the Fermi level. Valence band of Co 2 MnSn shows a large density of delocalized Co 3 d states present near the Fermi level. The Mn 3 d states are more localized and exist below the Fermi level. First principles calculations using density functional theory with GGA and GGA + U formalisms have been performed to understand and analyze the experimental results. The experimental density of states and magnetic moment show a good matching with the calculation carried out with on-site Coulomb correlation U of ∼3 eV on the Mn 3 d states. The presence of U on the Mn 3 d states also reduces the spin polarization at the Fermi level, which is one of the reasons for the observed low value of spin polarization reported for this system. [ABSTRACT FROM AUTHOR]

• The half-metallic and magnetic properties of Zr 2 CrAl were investigated. • The cubic, tetragonal, orthorhombic and rhombohedral structures were considered. • The total magnetic moment of Zr 2 CrAl, for all distortions analyzed is 1 μ B / f.u. • Complete spin polarization is present, in all crystal structures investigated. The research efforts focused on the implementation of Heusler materials into spintronic heterostructures triggered the investigations on the half-metallic and magnetic properties on Zr 2 CrAl ferrimagnetic compound. The theoretical investigations based on Density Functional Theory were performed on the tetragonal, orthorhombic and rhombohedral distortions of the typical inverse-Heusler cubic crystalline structure, previously reported. The compound exhibits half-metallic characteristics for all deformations considered. The slight variations in volume of the unit cell do not destroy the high spin polarization state. The band gap from minority spin channel slightly decreases in orthorhombic and rhombohedral deformations. The total magnetic moment calculated per formula unit is integer (equal to 1 μ B /f.u.) and follows the Slater-Pauling rule for all cases investigated. The antiferromagnetic coupling between the Zr and Cr atoms was preserved. The functionality of ferrimagnetic full-Heusler alloys to be used as overlayers in the production of epitaxially deposited heterostructures on substrates with crystalline structures other than cubic was proven. [ABSTRACT FROM AUTHOR]

• Above room temperature half metallic ferromagnetism. • Quantum spin of electrons leading the charge with multifunctional properties. • Exchange mechanism certifies the ferromagnetism by electron spin rather than clustering. • Half metallic ferromagnetism and 100% spin polarization. The recent development of electronic devices and control over their electro-magnetic and thermoelectric characteristics via electron spin has attracted a significant attention. Herein, we have addressed magnetic and thermoelectric calculations of K 2 MZ 6 (M = Os, Ir, and Z = Cl, Br) by quantum simulations. By comparing energies in antiferromagnetic, and ferromagnetic states, it turns out that lower energy corresponds to ferromagnetic (FM) states. Further, to confirm structural stability of FM state, tolerance factor was utilized. The Curie temperature has been reported by Heisenberg classical model. Moreover, the band structures (BS) and density of states (DOS) were analyzed to categorize half metallic (HM) ferromagnetism. To deeply understand the governing Half metallic ferromagnetism, the partial DOSs was tackled by p-d hybridization, exchange energies, and double-exchange model. The system is 100% spin polarized which is assured by integer magnetic moment. [ABSTRACT FROM AUTHOR]

• Above room temperature ferromagnetism, and spintronic applications. • Quantum spin of electrons dominant the charge with multifunctional properties. • Exchange mechanism certifies the ferromagnetism by electron spin instead of magnetic ion clustering. • Half metallic ferromagnetism and 100% spin polarization. • Large value of electrical conductivity and ultralow low values of thermal conductivity. The charge and spin degrees of freedom of electrons employed together introduce a new field of electronics, known as spintronics, which has multifunctional applications in data storage, control, and transfer in supercomputing. In this perspective, we have comprehensively investigated cubic double perovskites Rb 2 Z(Cl/Br) 6 (Z = Ta, W, Re). More precisely, we explored their structural, electronic, magnetic, and thermal transports. The structural stability is addressed by a tolerance factor, enthalpy of formation, and Curie temperature calculations. Half metallic ferromagnetism (HMF), quantum exchange process, spin polarization, and exchange energies are explained in terms of hybridization and double exchange mechanism. Furthermore, spin-polarized thermal transports are revealed by investigating thermal conductivity, Seebeck coefficient, and power factor. [ABSTRACT FROM AUTHOR]

Abstract: We have calculated the electronic and magnetic properties of 3d transition metal based full Heusler compounds Co2CrZ (Z=Ga, Ge, As), by using full potential linearized augmented plane wave (FP-LAPW) method. The calculated density of states (DOS) and band structure for Co2CrZ shows the existence of band gap in their minority-spin channel. The respective energy gaps of Co2CrGe and Co2CrGa are 0.24 and 0.38eV with their Fermi energies (E Fs) lie exactly at the gap. The compound Co2CrAs when treated with local spin density approximation (LSDA) does not show half metallic ferromagnetism (HMF) even though there exist a gap this is because the E F does not lie at the middle of the gap. We have considered Co2CrAs as strongly correlated system as Cr-d states at E F are strongly localized thus the system was treated in terms of the LSDA+U. The total magnetic moment of Co2CrAs was found to be an exact integer value 5.00 μ B within LSDA+U. We have also found that the total magnetic moments increase as the Z goes from Ga to As. [Copyright &y& Elsevier]

• Analysis of electronic structure, and magnetic and structural properties of model quaternary Heusler alloys ZrRhTiZ (Z = Al, In). • Unraveled chemical and thermodynamic stabilities allow for the synthesis of these compounds. • Exceeding room temperature Curie point provides a promise for beyond room temperature spintronics and magneto-electronics applications. • The effect of uniform strain inverts the band gap from one spin channel to another spin channel resulting exchange bias like effect. Electronic structure, and magnetic and structural properties of quaternary Heusler alloys ZrRhTiZ (Z = Al, In) have been analyzed from first principles calculations. The ferromagnetic ground state and thermodynamical stability of these compounds are supported by relative total energies, and by derived formation and cohesive energies, respectively. The investigated Curie temperatures of the compounds exceed room temperature indicating that these compounds are promising candidates for beyond room temperature spintronics and magneto-electronics applications. Both compounds follow the Slater-Pauling 18 electron rule and exhibit half-metallic ferromagnetic behavior with magnetic moments of 2 μ B with 100% spin polarization in one spin channel at the Fermi-level. The effect of uniform strain on half-metallicity of these compounds inverts the band gap from one spin channel to another spin channel with a mixed spin (magnetic moment) regime that can be mapped to an exchange bias like effect observed in some of the magnetic Heusler compounds. The half metallic ferromagnetic behavior is retained within −2 to 2% strain contrasting with the anomalous spin flip in −1% and 1% strain in ZrRhTiZ (Z = Al, In). [ABSTRACT FROM AUTHOR]

Structural, magnetic, mechanical, and thermal characteristics of equiatomic quaternary Heusler alloys (EQHA) FeTiVZ (Z = Ga, In) and FeZrVZ (Z = Ga, In) were examined by employing full potential – linearized augmented plane wave (FP-LAPW) scheme. The calculations for structural optimization were performed for three different types of structures based on atomic positions named as Type I (T I), Type II (T II) and Type III (T III). Geometry optimization results confirmed that T I is the most optimized structure as compared to other two types. The phase stability calculations confirmed the ferromagnetic (FM) nature of these Heusler alloys (HA). The magnetic characteristics have shown that the findings of band structures are agreed to the density of states (DOS). All these Fe-based HA have clear band gap (E g) in spin down (S ↓) channel which confirmed their half metallic (HM) nature and 100% spin polarization (S P). The S ↓ E g of FeTiVGa, FeTiVIn, FeZrVGa, and FeZrVIn is 0.33eV, 0.35eV, 0.90eV, and 0.84eV respectively. The elastic constants and other calculated mechanical parameters verify the mechanical stability of compounds except FeTiVIn which needs further investigation. Based on elastic constants, the calculated Debye temperature (θ D) , and melting temperature (T m) proves the thermodynamic stability of FeZrVZ (Z = Ga, In) and FeTiVGa. The obtained results have predicted that these alloys may be utilized in spintronic applications. • A new series of Fe-based QHA are examined by employing FP-LAPW scheme via WIEN2k code. • Fe-based EQHA are stable in FM phase with T I crystal structure. • These QHA have HM character and are completely spin polarized materials. • The calculated MM agrees to the Slater-Pauling rule. • FeTiVZ (Z = Ga, In) and FeZrVIn are mechanically stable QHA. [ABSTRACT FROM AUTHOR]

Based on the previous research and summary, a new half-metallic Heusler alloy FeCrAs have been proposed. The density functional theory of spin polarization is calculated by using the first-principles calculation software CASTEP to determine the lattice constants of FeCrAs compounds in half-Heusler structure. The effect of each element on its half-metallicity and the formation of band gap are calculated. The total magnetic moment is calculated and verified theoretically. The range of lattice distortion which keeps half -metallic properties was studied to ensure its half-metallic properties. In the calculation process, the role of Fe atom in the crystal cell, based on the theory of level splitting in the crystal field of the complexes, has been studied. According to the calculations, the FeCrAs compound of Half-Heusler phase is a new Heusler alloy. • A new half-metallic Heusler alloy FeCrAs has been proposed. • Energy level splitting and cobond hybridization of Fe and Cr atoms are explained. • d-states of 3d transition metals influence the formation of spin-down bandgap. [ABSTRACT FROM AUTHOR]

The structural stability, band structure, density of states (DOS), magnetic and mechanical properties of Co-based equiatomic quaternary Heusler alloys (EQHAs) CoYCrZ (Z = Si, Ge, Ga, Al) are examined by employing 1st principle calculations in the framework of density functional theory (DFT) as embedded in Wien2k code. The generalized gradient approximation (GGA) of Perdew-Burke Ernzehrof (PBE) is used for all these calculations. The lattice constants obtained by the optimization of structures and Type-II is found the most stable configuration for all alloys. The band diagrams and DOS calculations show that all these materials possess half metallic (HM) character because they have band gap in minority spin channel. The origin of band gap has been explained which is due to the robust d-d hybridization among transition metals (TMs). The obtained magnetic moments (MMs) are in accordance to the Slater-Pauling rule. The considered materials have high MMs and all alloys showed 100% spin polarization (SP). Curie temperature has also been calculated and reported for all these alloys. In order to check the mechanical stability, the calculations for elastic constants and other mechanical parameters are carried out which have revealed that all alloys are stable and have ductile nature. All the considered alloys in this study are reported for the first time and no data is available for comparison. It is envisaged these alloys are suitable for spintronic applications as in magnetic tunnel junctions (MTJs), spin valves, and spin injectors etc. • First principle study of EQHAs CoYCrZ (Z = Si, Ge, Ga, Al). • Calculations of structural stability, electronic, magnetic and elastic properties. • Calculations for FM, AFM and Non-magnetic phases. • Half metallic nature and high spin polarization. • Analysis of the origin of band gap. [ABSTRACT FROM AUTHOR]

Spin polarized structural, electronic and magnetic properties of new quaternary Heusler alloy CoZrIrSi have been studied using the first-principles calculation based on density functional theory. Interchanging the positions of atoms, the calculations were performed for three types of Heusler alloy CoZrIrSi. The results clearly showed that all three types of Heusler alloy CoZrIrSi were structurally stable in ferrimagnetic phase and their total spin magnetic moments (μ t = 2μ B /cell) were in accordance with Slater-Pauling rule. Based on investigation of structural properties of Heusler alloy CoZrIrSi, it was found that the type 2 structure of CoZrIrSi was more stable than others due to its lowest cohesive energy. Based on the results of studies undertaken on electronic properties of Heusler alloy CoZrIrSi using GGA-PBE calculations, it was clearly seen that the type 2 structure possessed half-metallic characteristic due to overlapping between conduction and valance band at the Fermi level only for spin-down channel. Thus, type 2 structure of CoZrIrSi had 100% spin polarization. It can be considered a good candidate for spintronics applications. • Three types of quaternary Heusler alloy CoZrIrSi were ferrimagnetic. • The type 2 structure had half-metal characteristic with 100% spin polarization. • The total spin magnetic moment of three types of Heusler alloy CoZrIrSi, was found in compliance with Slater-Pauling rule. [ABSTRACT FROM AUTHOR]