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To utilize highly spin-polarized Heusler alloys in practical spintronic devices, the realization of highly textured and structurally ordered polycrystalline thin films under limited annealing temperatures (TA) is critical. Compared to the natural [110]-texture of Heusler alloys, the [001]-texture is considered to be favorable for current-perpendicular-to-plane giant magnetoresistance devices due to the reduced lattice misfit with the face-centered-cubic Ag spacer layers. In this study, we fabricated [001]-oriented polycrystalline Co2FeGa0.5Ge0.5 (CFGG) Heusler alloy films epitaxially grown on a [001]-oriented polycrystalline Ag buffer layer on a thermally oxidized Si substrate, and the microstructure of the [001]-oriented Ag/CFGG bilayer film was investigated in detail. The [001]-oriented Ag films were obtained by introducing N2 into Ar during the sputtering process. The [001]-oriented CFGG films exhibited smooth interfaces, B2 ordering, and a high saturation magnetization close to the theoretical value under relatively low annealing at TA = 300 °C, which are critical for industrial applications such as read heads of hard disk drives. [ABSTRACT FROM AUTHOR]

Magnetic refrigeration working based on the magnetocaloric effect can be the perfect replacement of the conventional gas compression-based refrigeration technology and reduces its harmful effects on the environment. The boundary between a first-order and a second-order phase transition would be where the perfect magnetocaloric material would be found. Therefore, establishing the sequence of phase transitions clearly is essential for the characterization of other phase change materials and for applied magnetocaloric research. A quantitative fingerprint of second-order thermomagnetic phase transitions is reported here in Si-substituted high content Mn-based inverse Heusler alloy systems, which are found to be crystallized in cubic structures. The second-order nature of the phase transition has been confirmed from the Arrott plot analysis and a correlation between magnetocaloric effect and local exponent is established. Using the Arrott plot, the critical exponents are evaluated employing different techniques such as modified Arrott plot, Kouvel–Fisher method, and critical isotherm. Their values are found to be in great agreement with each other and follow the mean-field model signifying the presence of long-range ordering in the materials. The high value of isothermal magnetic entropy change and the reversibility justifies the suitability of the reported materials in the practical application as magnetic refrigerants. [ABSTRACT FROM AUTHOR]

Magnetic refrigeration is an active research area considering its potential to replace gas-based refrigeration systems, which are detrimental to the environment owing to chlorofluorocarbon emissions. Heusler alloys such as Ni2MnGa are known for their magnetocaloric effect, and addition of elements like Cu has increased the refrigeration capacity of the system. Magnetocaloric properties are a strict function of composition, and few alloy compositions in Mn–Ni–Cu–Ga can exhibit enhanced magnetocaloric properties. Most of the previous works have focused on Mn–Ni–Cu–Ga, and the enhancement of magnetocaloric properties is attributed to adding Cu. However, no magnetocaloric material has been reported in the Mn–Ni–Cu system, which could potentially show benefit from Cu addition. Hence, in the present study, thermodynamic optimization of the Mn–Ni–Cu-based ternary system and its three sub-binaries, Mn–Cu, Mn–Ni, and Ni–Cu, are performed using the CALculation of PHAse Diagram approach. In order to capture the liquidus in the Mn–Ni system and congruent transformation, a few alloy compositions were prepared and analyzed using differential thermal analysis. Using the current optimized database, temperatures are calculated as a function of Mn, Ni, and Cu compositions to ascertain the phase transition between the austenite and martensite phases, which occur around room temperature. [ABSTRACT FROM AUTHOR]

Magnetic materials with high negative spin polarization have been sought as a building block to increase the design freedom and performance of spintronics devices. In this paper, we investigate negative spin polarization of Mn2VGa Heusler alloy in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices. We fabricated an epitaxial CPP-GMR stack consisting of Mn2VGa/Ag/CoFe with L21 ordering in the Mn2VGa layer and observed negative magnetoresistance (MR), which provided evidence of negative spin polarization. The MR ratio depended on thermal treatments (deposition at an elevated temperature and post-annealing), because these processes affected the ordering, roughness, and magnetic properties of Mn2VGa. The maximum MR ratio reached −1.8% at room temperature and −3.0% at low temperatures, representing the highest among the negative MR values in pseudo-spin-valve CPP-GMR devices despite the underestimation due to an incomplete antiparallel magnetization configuration. These findings demonstrate the potential of Mn2VGa for a material with high negative spin polarization. [ABSTRACT FROM AUTHOR]

Alloying heavy metals (HMs) has been an effective method for enhancing the efficiency of spin–orbit torque. In this study, we demonstrate that Pt100−xWx/Pt/Co/Ta multilayers still maintain perpendicular magnetic anisotropy after high-temperature annealing. Doping tungsten (W) into HM platinum (Pt) at the bottom of a Pt/Co/Ta multilayer significantly increases the spin Hall angle (θ S H ) and reduces the critical switching current density (Jc). The harmonic Hall test results show that the θ S H of the Pt88W12 alloy film is approximately 0.29, which is higher than that of the pure Pt film (0.15). The magnetization switching test reveals that the Jc of Pt94W6 alloy film is approximately 4.892 × 106 A/cm2, which is 51.9% lower than that of the pure Pt film. This study offers a valuable method for reducing power consumption and enhancing the efficiency of related application devices. [ABSTRACT FROM AUTHOR]

We investigate the magnetic behavior and critical exponents of quaternary CoFeV 0.8 Mn 0.2 Si Heusler alloy to understand the interactions across the Curie temperature (T C ). The Rietveld refinement of the x-ray diffraction pattern with the space group F 4 ¯ 3m confirms a single-phase cubic Y-type crystal structure. The magnetic susceptibility χ (T) data show a ferromagnetic nature with a second-order phase transition from paramagnetic to ferromagnetic at 446 ± 1 K. The saturation magnetization at 5 K is found to be 2.2 μ B /f.u., which is close to the Slater–Pauling rule and indicates its half-metallic nature. The values of asymptotic critical exponents (β , γ , and δ) and the T C are extracted through detailed analytical analysis including the modified Arrott plot, the Kouvel–Fisher (K–F) method, and the Widom scaling relation. Interestingly, the estimated values of β = 0.369 and γ = 1.445 closely approximate the theoretical values of the 3D Heisenberg model across the T C and validate the second-order thermodynamic phase transition. The obtained exponents lead to the collapse of renormalized isotherms, represented by the relationship between the magnetization (m) and the applied magnetic field (h), into two distinct branches above and below the T C , which validates the reliability of the analysis. Furthermore, these exponents suggest that the spin interaction follows a decay pattern of J (r) ∼ r − 4.99 , indicating a short-range magnetic ordering, akin to the itinerant-electron 3D Heisenberg model. [ABSTRACT FROM AUTHOR]

We report an investigation into the substantially large and customizable exchange anisotropy (HEA) and coercivity (HC) in a set of bottom-pinned Ir7Mn93/Co2FeAl bilayer heterostructures fabricated using ion-beam sputtering at room temperature (RT) in the presence of an in-situ in-plane static magnetic field of 1 kOe. This modulation is achieved by controlling the microstructural parameter (i.e., grain diameter) of the antiferromagnetic (AF) Ir7Mn93 (IrMn) layer. These bilayers revealed strong positive exchange anisotropy (PEA) at RT, while negative exchange anisotropy (NEA) became evident when field-cooled to 15 K in the presence of 3 kOe. By systematically controlling the AF grain diameter from ∼5.39 to ∼6.94 nm, the PEA and NEA were found to increase by a factor of ∼2.1 and ∼1.8, respectively. However, once the AF grain diameter exceeded the necessary threshold for thermal stability, further enhancement in grain diameter above ∼6.94 nm led to a reduction in both HEA and HC. This decrease was attributed to a reduction in pinning centers at the AF/FM (ferromagnet) interface. The training data are fitted by utilizing various theoretical models, such as thermal relaxation, Binek's model, and spin relaxation model. The spin relaxation model was found to be applicable to fit the complete range of training data, encompassing both thermal and athermal decay, within the context of frozen and rotatable spins. [ABSTRACT FROM AUTHOR]

We report on the field evolution of the microwave spin wave modes in magnonic crystals made of square antidot lattices etched in a thin film of the Co2MnSi Heusler alloy and having a lateral size s of 200 nm and an edge-to-edge separation d of 600 or 800 nm. The spin wave modes are investigated combining ferromagnetic resonance, Brillouin light scattering experiments, and micromagnetic simulations of the static and dynamic magnetic states as a function of the applied field. We show that for applied fields ≥10 mT, when the magnetization is quasi-saturated across the crystals, the two samples show similar behavior and the two most intense modes in the spin waves spectra correspond to a mode extending in the channels comprised between the antidot and a mode localized in the region between the antidots. For smaller fields, we observe a difference of the measured spectra as a function of d. This is attributed to the fact that for d = 800 nm, the magnetization remains partially uniform in the channel between the antidots because of the Heusler cubic crystal anisotropy, while for d = 600 nm, the magnetic edge domains around the antidots spread into the channels. Moreover, this anisotropy also allows different remanent states when initializing the crystals with a small magnetic field along two perpendicular directions. This leads to an efficient excitation or extinction of the spin wave modes, making possible to achieve reconfigurable microwave devices exploiting an antidot geometry in a metallic ferromagnetic with a low damping coefficient. [ABSTRACT FROM AUTHOR]

Heusler alloy-based magnetic tunnel junctions have the potential to provide high spin polarization, small damping, and fast switching. In this study, junctions with a ferromagnetic electrode of Co2FeAl were fabricated via room-temperature sputtering on Si/SiO2 substrates. The effect of boron doping on Co2FeAl magnetic tunnel junctions was investigated for different boron concentrations. The surface roughness determined by atomic force microscope, and the analysis of x-ray diffraction measurement on the Co2FeAl thin film reveals critical information about the interface. The Co2FeAl layer was deposited on the bottom and on the top of the insulating MgO layer as two different sample structures to compare the impact of the boron doping on different layers through tunneling magnetoresistance measurements. The doping of boron in Co2FeAl had a large positive impact on the structural and magneto-transport properties of the junctions, with reduced interfacial roughness and substantial improvement in tunneling magnetoresistance. In samples annealed at low temperature, a two-level magnetoresistance was also observed. This is believed to be related to the memristive effect of the tunnel barrier. The findings of this study have practical uses for the design and fabrication of magnetic tunnel junctions with improved magneto-transport properties. [ABSTRACT FROM AUTHOR]

Intercalation has attracted considerable attention due to its extensive ability to modify the electronic, optical, and magnetic properties of two-dimensional (2D) layered nanomaterials. Typically, dispersed atoms or molecules are inserted into the van der Waals gap of the 2D materials. Recently, Guo et al. experimentally reported the novel VS2–VS superlattice, where the intercalation takes the form of atomic chain arrays. In this study, we employed the first-principles calculations based on density functional theory to investigate a series of analogous 2D MX2–MX–MX2 nanomaterials, which, consisting of 2D transition metal dichalcogenide bilayers, intercalated with a one-dimensional transition metal chalcogenide MX chain array, forming a hotdog-like structure. Some of the 2D MX2–MX–MX2 are thermally and dynamically stable, suggesting their potential for experimental fabrication similar to VS2–VS–VS2. MnS2–MnS–MnS2 and MnSe2–MnSe–MnSe2 have been found to exhibit ferromagnetic half-metallic properties. In addition, VSe2–VSe–VSe2, CrS2–CrS–CrS2, and CrSe2–CrSe–CrSe2 have been found to be thermally and dynamically stable. Under appropriate external stress, doping, or bias, they could become ferromagnetic half-metals, revealing their potential for spintronic applications. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the spin transport properties of binuclear manganese phthalocyanine (M n 2 P c 2) spintronic devices sandwiched between two nickel electrodes using the non-equilibrium Green's function method in combination with density functional theory. Based on the calculation results, the M n 2 P c 2 device exhibited excellent spin-filtering capabilities, demonstrating an exceptionally high spin filter efficiency (SFE). Irrespective of the parallel or antiparallel orientation of magnetization in the electrodes, we observed that when both manganese atoms were in a spin-up state, the SFE of spin-resolved currents under finite bias and the thermoelectric currents induced by temperature gradients at fixed temperatures were both close to 100%. The large spin Seebeck polarization of the M n 2 P c 2 device was also obtained at low reference temperatures. This study explores the potential for developing multifunctional spintronic single-molecule devices using Ni − M n 2 P c 2. [ABSTRACT FROM AUTHOR]

Spin gapless semiconductor (SGS) has attracted much attention since its theoretical prediction, while concrete experimental hints are still lacking in the relevant Heusler alloys. Here in this work, by preparing the series alloys of Mn2CoGa1−xAlx (x = 0, 0.25, 0.5, 0.75, and 1), we identified the vanishing of the anomalous Hall effect in the ferromagnetic Mn2CoGa (or x = 0.25) alloy in a wide temperature interval, accompanying with growing contribution from the ordinary Hall effect. As a result, comparatively low carrier density (1020 cm−3) and high carrier mobility (150 cm2/V s) are obtained in the Mn2CoGa (or x = 0.25) alloy in the temperature range of 10–200 K. These also lead to a large dip in the related magnetoresistance at low fields. However, in a high Al content, although the magnetization behavior is not altered significantly, the Hall resistivity is, instead, dominated by the anomalous one, just analogous to that widely reported in Mn2CoAl. The distinct electrical-transport behavior of x = 0 and x = 0.75 (or 1) is presently understood by their possible different scattering mechanism of the anomalous Hall effect due to the differences in the atomic order and conductivity. Our work can expand the existing understanding of the SGS properties and offer a better SGS candidate with higher carrier mobility that can facilitate the application in the spin-injected related devices. [ABSTRACT FROM AUTHOR]

The cobalt-based full Heusler alloy Co2MnGa (CMG) is well known for exhibiting an exotic phenomenon such as magnetic Weyl semimetallic nature with a high Curie temperature of ∼700 K and a giant anomalous Hall effect. Here, we report a detailed study of structural, electrical, and magnetic properties of Co2MnGa thin films (thickness in the 40–10 nm range) grown on Si(100) by the direct-current magnetron co-sputtering technique using Co and MnGa targets. Structural analysis of the samples revealed the polycrystalline nature of these films with B2 type structural ordering. The damping parameter decreases with the increase in film thickness and reaches the minimum value of 6.1 × 10−3 for a 40 nm thin CMG film. These CMG films are magnetically isotropic and soft ferromagnetic in nature. A remarkably high value of anomalous Hall conductivity (AHC) of 1920 S/cm (2 K) is found for the 40 nm thin film, which is comparable to earlier reported values on highly ordered CMG films. Nearly 73% of this AHC value originates from the intrinsic contribution. The AHC and longitudinal conductivity both increase with the film thickness. Different scaling mechanisms are used to compute the intrinsic and extrinsic contributions playing a role in AHC. The analysis of advanced scaling [by Tian et al., Phys. Rev. Lett. 103, 1–4 (2009)] performed on these CMG films suggests the consistency in the enhanced intrinsic AHC value irrespective of the thickness and a decrease in skew scattering contribution with thickness. These results will enhance the understanding about the magnetic and transport properties of Co2MnGa thin films of different thicknesses and suggest it to be a promising material for topospintronic applications. [ABSTRACT FROM AUTHOR]

We present computational results on electronic, magnetic, and structural properties of CoVMnSb, a quaternary Heusler alloy. Our calculations indicate that this material may crystallize in two energetically close structural phases: inverted and regular cubic. The inverted cubic phase is the ground state, with ferrimagnetic alignment, and around 80% spin polarization. Despite having a relatively large bandgap in the minority-spin channel close to the Fermi level, this phase does not undergo a half-metallic transition under pressure. This is explained by the "pinning" of the Fermi level at the minority-spin states at the Γ point. At the same time, the regular cubic phase is half-metallic and retains its perfect spin polarization under a wide range of mechanical strain. Transition to a regular cubic phase may be attained by applying uniform pressure (but not biaxial strain). In practice, this pressure may be realized by an atomic substitution of non-magnetic atoms (Sb) with another non-magnetic atom (Si) of a smaller radius. Our calculations indicate that 25% substitution of Sb with Si results in a half-metallic regular cubic phase being the ground state. In addition, CoVMnSb0.5Si0.5 retains its half-metallic properties under a considerable range of mechanical pressure, as well as exhibits thermodynamic stability, thus making this alloy attractive for potential spintronic applications. We hope that the presented results will stimulate experimental efforts to synthesize this compound. [ABSTRACT FROM AUTHOR]

A nanoporous Cu 2 TiSn Heusler alloy is prepared by dealloying-induced phase transformation for electrocatalytic nitrate reduction in neutral conditions and to achieve value-added ammonium phosphomolybdate. [Display omitted] Heusler alloys are a series of well-established intermetallic compounds with abundant structure and elemental substitutions, which are considered as potentially valuable catalysts for integrating multiple reactions owing to the features of ordered atomic arrangement and optimized electronic structure. Herein, a nanoporous copper titanium tin (np-Cu 2 TiSn) Heusler alloy is successfully prepared by the (electro)chemical dealloying transformation method, which exhibits high nitrate (NO 3 –) reduction performance with an NH 3 Faradaic efficiency of 77.14 %, an NH 3 yield rate of 11.90 mg h−1 mg−1 cat , and a stability for 100 h under neutral condition. Significantly, we also convert NO 3 − to high-purity ammonium phosphomolybdate with NH 4 + collection efficiency of 83.8 %, which suggests a practical approach to convert wastewater nitrate into value-added ammonia products. Experiments and theoretical calculations reveal that the electronic structure of Cu sites is modulated by the ligand effect of surrounding Ti and Sn atoms, which can simultaneously enhance the activation of NO 3 −, facilitate the desorption of NH 3 , and reduce the energy barriers, thereby boosting the electrochemical nitrate reduction reaction. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive analysis of the stability of Ru2VGe1-xSix for x = [0, 0.25, 0.5, 0.75, 1] compounds using a first-principle full-potential linearized augmented plane wave method implemented in a computational code based on WIEN2k. The article sheds light on the behavior of different concentrations of Si and their impact on the magneto-structural, thermodynamic, and mechanical stability, resulting in the prediction of five compounds with varying magnetism based on their compositions, including Fm-3 m cubic for Ru2VGe and Ru2VSi, Pm-3 m cubic structure for x = 0.25, 0.75, and P4/mmm tetragonal structure for x = 0.5. A tiny energy difference between phases may lead to a low magnetic transition temperature TMFA for all compounds except the tetragonal one, which keeps the antiferromagnetic phase above room temperature. Their formation and cohesive energies prove their stability. A regular solution model was used to investigate the thermodynamic stability of the alloys, revealing a miscibility gap at a composition range of 0.537 ≤ x ≤ 1, with the critical temperature of Tc = 986.24 K at a specific composition of xC = 0.801. The elastic properties showed the compounds are stable against external stresses and deformations with ductility and good thermal conductivity, hardness, and machinability. The anisotropy behavior moves from anisotropic in Ru2VGe to semi-isotropic by Si substitution. [ABSTRACT FROM AUTHOR]

A theoretical study of magnetic, electronic structure, mechanical and thermodynamic properties of Cr2TaZ (Z = Al, Ga and Sb) Heusler alloys has been extensively investigated by the full-potential linearized augmented plane wave (FP-LAPW) method with the Generalized Gradient Approximation (GGA). Structural parameters such as lattice constant (a) , bulk modulus (B) and first pressure derivative of bulk modulus (B ,) were obtained by using the Murnaghan equation. The calculated lattice constants for Cr2TaAl, Cr2TaGa and Cr2TaSb alloys are for 61,029, 61,170 and 60,795 Å, respectively. It is found that the L21-type (AlCu2Mnl-type) structure is energetically more stable than the X-type (CuHg2Ti-type) structure due to the lower total energy. The results of elastic constants robustness show that the mechanical stability of Cr2TaZ (Z = Al, Ga and Sb) can be well-maintained. The calculated electronic band structure reveals the metallic nature of Cr2TaZ (Z = Al, Ga and Sb) and its total magnetic moment of 2.00 μ B is mainly contributed by Cr atom from strong spin splitting effect, as indicated with the distinctive distributions of the density of states in two spin directions. Furthermore temperature and pressure dependence of thermodynamic properties of these materials have been examined in the ranges (0–1400 K) and (0–25 GPa), respectively. [ABSTRACT FROM AUTHOR]

Most of the ferromagnetic shape memory (FSM) Heusler alloys, which are primarily studied in bulk form in the literature, exhibit p-d type hybridization. This study conducts a thorough multidirectional investigation of a strongly d-d hybridized quinary melt-spun annealed ribbon having the composition Ni35Mn34.5Co14Fe1Ti15.5 (NMCFT-1). This off-stoichiometric, polycrystalline FSM, fabricated using the melt-spin technique, exhibits a highly textured microstructure, double magnetic transitions and super-mechanical features mitigating brittleness. It crystallizes in a perfectly B2-type disorder austenite (Pm-3m, space group number 221) phase at room temperature. It has been hypothesized that geometric frustration is the causative factor for this disorder. Curie temperature of austenite phase ( T C A ) between paramagnetic → ferromagnetic state is found to be ∼364.57 K, whereas martensite transformation temperature from weak magnetic martensite state to ferromagnetic austenite state is ∼174.74 K. Calculated moments (effective moment, μ eff = 5.12 μ B ; low-temperature saturation moment, μ S (or M S (0) ) = 5.08 μ B ) yield a Rhodes–Wohlfarth ratio of ∼1, indicating the existence of the non-itinerant nature of 3d electrons, whereas the ferromagnetism and the linear or non-linear dependency of M s 2 (T ) on T 2 around T C A indicates the presence of long-range Rudermann–Kittel–Kasuya–Yosida-type interaction. More importantly, the maximum magnetic entropy change ( Δ S m ) obtained across the first-order magneto-structural transition and second-order magnetic transition are +18.2 J·kg−1K−1 at 6 T and −8.8 J·kg−1K−1 at 2 T, respectively, while a very high working temperature span (Δ T FWHM) of 28.561 K and 6.922 K are found for the same condition. The sample exhibits a significant relative cooling power of 402.98 J·kg−1 at a magnetic field of 6 T across the FOMT and 60.19 J·kg−1 at a 2 T field across the SOMT, respectively, along with excellent mechanical features such as a Vickers hardness (HV) of 411.80 HV (∼4.04 GPa). Meanwhile, Chen's super hard model fails to predict the ribbon's HV value, but Miao's hard model does, indicating that the ribbon is hard but not super hard. It also paves the way for additional investigation into innovative FSMs like this. [ABSTRACT FROM AUTHOR]

In this study, we report on the detailed atomic ordering, magnetic and electrical properties of the Heusler alloy Mn2CoAl, studied via combined experimental methods and a theoretical calculation approach. Our studies confirm the Hg2CuTi-type crystal structure of Mn2CoAl with 25% anti-site disorder between Mn (B:1/4,1/4,1/4) and Co(C:1/2,1/2,1/2) sites. Neutron powder diffraction measurements identify the antiparallel spin couplings between Mn:A↓ and Mn:B↑, Co:C↑, resulting in a ferrimagnetic structure with a net magnetic moment of ∼1.6 μ B at room temperature. In terms of the electronic calculations, we find that the anti-site atoms will contribute large densities of states at the Fermi level, thus destroying the spin gapless band structure and making Mn2CoAl a normal ferrimagnetic metal. This report is intended to establish a basic understanding of the structure and physical properties of Mn2CoAl. [ABSTRACT FROM AUTHOR]

Most of the ferromagnetic shape memory (FSM) Heusler alloys, which are primarily studied in bulk form in the literature, exhibit p-d type hybridization. This study conducts a thorough multidirectional investigation of a strongly d-d hybridized quinary melt-spun annealed ribbon having the composition Ni35Mn34.5Co14Fe1Ti15.5 (NMCFT-1). This off-stoichiometric, polycrystalline FSM, fabricated using the melt-spin technique, exhibits a highly textured microstructure, double magnetic transitions and super-mechanical features mitigating brittleness. It crystallizes in a perfectly B2-type disorder austenite (Pm-3m, space group number 221) phase at room temperature. It has been hypothesized that geometric frustration is the causative factor for this disorder. Curie temperature of austenite phase ( T C A ) between paramagnetic → ferromagnetic state is found to be ∼364.57 K, whereas martensite transformation temperature from weak magnetic martensite state to ferromagnetic austenite state is ∼174.74 K. Calculated moments (effective moment, μ eff = 5.12 μ B ; low-temperature saturation moment, μ S (or M S (0) ) = 5.08 μ B ) yield a Rhodes–Wohlfarth ratio of ∼1, indicating the existence of the non-itinerant nature of 3d electrons, whereas the ferromagnetism and the linear or non-linear dependency of M s 2 (T ) on T 2 around T C A indicates the presence of long-range Rudermann–Kittel–Kasuya–Yosida-type interaction. More importantly, the maximum magnetic entropy change ( Δ S m ) obtained across the first-order magneto-structural transition and second-order magnetic transition are +18.2 J·kg−1K−1 at 6 T and −8.8 J·kg−1K−1 at 2 T, respectively, while a very high working temperature span (Δ T FWHM) of 28.561 K and 6.922 K are found for the same condition. The sample exhibits a significant relative cooling power of 402.98 J·kg−1 at a magnetic field of 6 T across the FOMT and 60.19 J·kg−1 at a 2 T field across the SOMT, respectively, along with excellent mechanical features such as a Vickers hardness (HV) of 411.80 HV (∼4.04 GPa). Meanwhile, Chen's super hard model fails to predict the ribbon's HV value, but Miao's hard model does, indicating that the ribbon is hard but not super hard. It also paves the way for additional investigation into innovative FSMs like this. [ABSTRACT FROM AUTHOR]

In this article, we have conducted a comprehensive study on the structural, mechanical, electronic, magnetic and thermodynamic properties of the Heusler alloys FeZrTiZ ( Z = A l , G a , G e ). Our investigation utilize the GGA exchange correlational approximation functional. The results of our analysis indicate that among the Y1-, Y2- and Y3-type structures, the Y1-type structure exhibits stability and demonstrates ferromagnetic behavior. Furthermore, mechanical property analysis reveals that all alloys possess ductile characteristics. The analysis of the density of states of the Heusler alloys FeZrTiZ ( Z = A l , G a , G e ) demonstrates the presence of half-metallic nature in all of the alloys. Additionally, the investigated Heusler alloys exhibit integer spin magnetic moments. To study thermodynamic properties, we use quasi-harmonic approximation, which allows to analyze specific heat capacity, thermal expansion, Debye temperature, vibrational free energy, internal energy and entropy of the Heusler alloys FeZrTiZ ( Z = A l , G a , G e ). Overall, our findings provide a clear understanding of the structural, mechanical, electronic, magnetic and thermodynamic characteristics of Heusler alloys FeZrTiZ ( Z = A l , G a , G e ), shedding light on their potential applications in spintronics. [ABSTRACT FROM AUTHOR]

This study investigates polycrystalline samples of TiFe2−xRexSn (with x = {0, 0.02, 0.04, 0.06, 0.2}) synthesized using conventional arc-melting and spark plasma sintering. Structural and morphological analysis shows that low Re substitutions result in good phase purity with minor traces of secondary phases, while higher Re content leads to the segregation of additional phases. The magnetism and electrical resistivity of the samples are affected by inherent Fe–Ti atomic disorder, with the effects of secondary phases becoming more prominent in the samples with higher Re content. The Seebeck coefficient values increase only for TiFe1.98Re0.02Sn, while the power factor increases for x = {0, 0.02, 0.04}, reaching maximal values for x = 0.02 at ~ 300 K and x = 0.04 at ~ 325 K, i.e., (2.22 ± 0.2) × 10−4 Wm−1 K−2. The thermal conductivity of the samples increases with x, resulting in modest values of the figure of merit, with the maximum achieved for x = 0.02 at 325 K, i.e., 0.015 ± 0.002. [ABSTRACT FROM AUTHOR]

We present the theoretical and experimental results for the full Heusler alloys Mn2MAl for late 3d transition metals – M = Fe, Co, Ni. For the first time, the synthesized Mn2CoAl and Mn2NiAl alloys crystallize in the β-Mn- and B2-types crystal structure. The electronic structure and magnetic properties of the alloys were investigated within the framework of first-principles theoretical calculations. It was revealed that the alloys have metallic properties and antiparallel alignment of the large Mn magnetic moments and almost compensated total magnetic moments. In addition, we investigated the effect of electronic correlations on the electronic structure and magnetic properties of the alloys within DFT + U method that resulted in a negligible effect for the total magnetic moments of Mn2MAl (M = Fe, Co, Ni). The frequency dependence of the real and imaginary parts of the dielectric constant is measured in the spectrum region of 0.1–5 eV. In order to characterize thermoelectric properties of the studied Heusler alloys, we performed measurements of electrical resistivity and calculated Seebeck coefficient. The results are interpreted based on our theoretical calculations and different structural compositions. [ABSTRACT FROM AUTHOR]

The structure and magnetic properties of epitaxial Heusler alloy films (Co2FeGe) deposited on MgO (100) substrates were investigated. Films of 60 nm thickness were prepared by magnetron co-sputtering at different substrate temperatures (TS), and those deposited at room temperature were later annealed at various temperatures (Ta). X-ray diffraction confirmed (001) [110] Co2FeGe || (001) [100] MgO epitaxial growth. A slight tetragonal distortion of the film cubic structure was found in all samples due to the tensile stress induced by the mismatch of the lattice parameters between Co2FeGe and the substrate. Improved quality of epitaxy and the formation of an atomically ordered L21 structure were observed for films processed at elevated temperatures. The values of magnetization increased with increasing TS and Ta. Ferromagnetic resonance (FMR) studies revealed 45° in-plane rotation of the easy anisotropy axis direction depending on the degree of the tetragonal distortion. The film annealed at Ta = 573 K possesses the minimal FMR linewidth and magnetic damping, while both these parameters increase for another TS and Ta. Overall, this study underscores the crucial role of thermal treatment in optimizing the magnetic properties of Co2FeGe films for potential spintronic and magnonic applications. [ABSTRACT FROM AUTHOR]

Magnetic refrigeration is an option to replace conventional refrigeration. There are many studies that analyze materials with magnetocaloric effect during the first cooling-heating cycle, without analyzing the influence of cycling (necessary to check its applicability). In this work, we proceed to analyze the crystallographic structure (X-Ray diffraction) and the thermal (differential scanning calorimetry) and thermomagnetic (PPMS cycles and ZFC–FH–FC scans) response after a hundred thermal cycles of two Heusler alloys, Ni49Mn36Sn14Pd1 and Ni48Mn36Sn14Pd2 (at.%), that have been produced by melt spinning as ribbon flakes. In order to check its stability from cycling, these ferromagnetic alloys have been subjected to a hundred of thermal cycles (heating/cooling to provoke the austenite to martensite reversible transformation. The comparison before and after cycling behavior allow us to state that the reduction of the crystallographic defects favors higher atomic order. Likewise, the thermodynamic parameters (entropy and enthalpy) and the magnetic response have been reduced at about 10–12%. [ABSTRACT FROM AUTHOR]

In this study, we investigate the effect of temperature on the performance of a read sensor by utilizing an atomistic model coupled with a spin transport model. Specifically, we study the temperature dependence of spin transport behavior and MR outputs in a Co 2 FeAl 0.5 Si 0.5 (CFAS)(5nm)/Cu(5nm)/CFAS(5nm) trilayer with diffusive interfaces. Initially, the two-channel model of spin-dependent resistivity is used to calculate the temperature dependence of spin transport parameters which serves as essential input for the spin accumulation model. Our findings demonstrate that as the temperature increases, the spin transport parameters and magnetic properties decrease due to the influence of thermal fluctuation. At a critical temperature, where the ferromagnet transitions to a paramagnetic state, we observe zero spin polarization. Furthermore, at elevated temperatures, the spin accumulation deviates from the equilibrium value, leading to a reduction in the magnitude of spin current and spin transport parameters due to thermal effects. As a consequence, the MR ratio decreases from 65% to 20% with increasing temperature from 0 to 400 K. Our results are consistent with previous experimental measurements. This study allows to deeply understand the physical mechanism in the reader stack which can significantly benefit reader design. [ABSTRACT FROM AUTHOR]

Density functional theory with pesudo potential approximation is used to study XBaB (X = Li , Na, K) half-Heusler compounds structural, magnetic and electrical property using Quantum espresso code and thermoelectric properties were studied using BoltzTrap code. Total energy calculations were carried out in the α , β and γ phases of XBaB compounds in C 1 b type structure. The compounds were stable in α -phase and hence further calculations were focused only on α phase. From the spin polarization calculations, magnetic state was stable than nonmagnetic state and exhibits ferromagnetism at the equilibrium lattice constant with an integer magnetic moment of 2  μ B . From the band structure calculations and through density of states, all the three compounds exhibit half-metallicity with 100% spin polarization by showing semi-conductivity for majority spin and metallicity for minority spin. In addition, thermoelectric properties were investigated for all three compounds. LiBaB is found to have high Seebeck coefficient of 2462 μ VK − 1 and ZT value of 1, compared to other compounds. These materials were found to have high ZT value and hence they can be used for thermoelectric applications. [ABSTRACT FROM AUTHOR]

We report the presence of electron-spin-phonon interactions in half-metallic ferromagnetic Sr2FeMoO6 (SFMO) double perovskite thin films using temperature-dependent Raman spectroscopy. A series of SFMO thin films have been prepared on LaAlO3 (001) single-crystal substrate using the Pulsed Laser Deposition technique. These depositions have been made in different gas-conditions such as in vacuum, and under nitrogen and oxygen gas pressures. At room temperature, Raman spectra manifest a Fano feature which indicates the presence of electron-phonon coupling in the films. The electron-phonon coupling strength further changes with a change in deposition conditions. Magnetization results show that the SFMO film grown in vacuum has the highest saturation magnetization which suggests better cation ordering as compared to the other films. For enhanced understanding, Raman spectra were recorded at varied temperatures and the data were analyzed by theoretical model fittings. A parameter quantifying temperature-dependent anharmonic nature of phonons has been derived using Balkanski model fits. This parameter shows a drastic deviation in the vicinity of Curie temperatures, manifesting a spin-phonon coupling in SFMO films. We further show that the spin-phonon coupling strengthens with improved Fe–Mo ordering. Any experimental observation of spin-phonon coupling has not been reported for SFMO systems till date. The magnetization data corroborate well with these observations made by Raman measurements. Our results of Raman spectroscopy, magnetization and resistivity collectively suggest that the SFMO films exhibit electron-spin-phonon interactions, which are influenced by the cation ordering. We also devised out the method of relating the anharmonic nature of Raman modes with the degree of Fe–Mo ordering and spin-phonon coupling in double-perovskite materials. [ABSTRACT FROM AUTHOR]

We studied the structural, electronic, mechanical, and thermodynamic properties of N2CaNa full Heusler alloys using density functional theory (DFT). Results for the structural analysis establish structural stability with a minimum formation energy of 29.9 eV. The compound is brittle and mechanically stable, having checked out with the Pugh criteria. The B/G ratio of bulk modulus B to shear modulus G for N2CaNa is 4.766, hence the material is ductile. N2CaNa alloy is ductile in nature. The Debye model correctly predicts the low-temperature dependence of heat capacity, which is proportional to Debye's T 3 law. Just like the Einstein model, it also recovers the Dulong–Petit law at high temperatures, suggesting the thermodynamic stability of the compounds at moderate temperatures. The results demonstrate potential N2CaNa for applications in spintronics, structural engineering, and other fields requiring materials with tailored properties. [ABSTRACT FROM AUTHOR]

In this work, we report on CoMnSi half‐Heusler alloy as a cathode material for secondary lithium‐ion batteries using ab initio methodology based on the density functional theory. The first‐principle calculations have been performed via the Wien2k package, which utilizes the full potential linearized augmented plane wave (FP‐LAPW) method to estimate the stability of the proposed structures and electronic characteristics while considering the exchange and correlation effects within the generalized gradient approximation. This alloy is found structurally stable with better electronic properties and with the alloying of lithium (Li) into the host lattice of CoMnSi, the metallic character is attained for LixCo1−xMnSi (0.125 ≤ x ≤ 1). We propose possible reactions at electrodes during the electrochemical lithiation. The addition of Li in place of the Co atom is found to be an endothermic process. With the increase in lithium concentration, a substantial change in the total and atom projected density of states around the Fermi level is observed. The theoretical maximum specific capacity (CM) and theoretical open circuit voltage (OCV) increase with the increase of lithium concentration in CoMnSi. The CM and OCV values attain a maximum value of around 297 mAh/g and 2.4 Volts for x ≥ 0.75, which means towards the complete conversion of CoMnSi into LiMnSi. The LiMnSi exhibits a similar structure as CoMnSi, which is also advantageous for the overall performance of lithium‐ion batteries to avoid any volumetric change during the charging and discharging cycles. Hence, the proposed half‐Heusler alloys have great potential to be used as a cathode material for lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

The effect of substituting Sn with a fourth element on the functional properties of Heusler NiMnSn alloys has been reported in the literature. In the present work, the influence of the addition of Si to the Heusler NiMnSn system was evaluated, where Ni44Mn44Sn12 (at.%), Ni44Mn44Sn10.5Si1.5 (at.%) and Ni44Mn44Sn9Si3 (at.%) alloys were prepared in an induction furnace without a controlled atmosphere, and were later characterized by optical microscopy, Vickers microhardness, electrical resistivity, and vibrating sample magnetometry. The results revealed that the partial replacement of Sn by 3 at.% Si did not modify the dendritic microstructure and the phases present at room temperature; however, it increased the percentage of the martensite phase from 51% to 76%. This modification in the percentage of this phase is responsible for reducing the average Vickers microhardness values (from 469 HV to 459 HV), increasing the electrical resistivity (from 1.3 mΩ mm to 2.21 mΩ mm), and decreasing the saturation magnetization (from 23.67 emu/g to 19.34 emu/g), coercivity (from 5.56 Oe to 5.14 Oe), and remanent magnetization (from 0.21 emu/g to 0.18 emu/g). With this, our results bring to light a new alternative for doping the NiMnSn alloy as a way of modifying the structural and electrical properties, constituting interesting parameters for technological applications. [ABSTRACT FROM AUTHOR]

The shape memory capabilities of Heusler alloy microwires with two different contents of Fe element instead of Ga element following step-by-step ordering heat treatment were explored based on the stoichiometric ratio of Ni2MnGa. The melt-drawing technique was used to create the polycrystalline microwires, and the two microwires had Fe atomic contents of 4.7 at.% and 5.5 at.%, respectively. The field emission scanning electron microscope was used to analyze the microwire's surface condition as well as the microscopic tensile fracture morphology. Using an X-ray diffractometer, the microwires' crystal structure was identified for phase analysis. Differential scanning calorimetry was used to examine the microwires' behavior during martensitic transformation. Using a dynamic mechanical stretcher, the elongation and recovery rate of microwires' one- and two-way shape memory behavior were examined. The findings demonstrated that the microwire phase structure, martensitic transformation behavior, and shape memory capabilities all displayed good properties after the heat treatment was ordered. [ABSTRACT FROM AUTHOR]

Memory shape magnetic alloys, especially Heusler alloys, are important materials in replacing conventional cooling with magnetic systems. In the present study off stoichiometric Heusler alloys with nominal composition Χ50Υ25+xΖ25‐x (X = Ni; Y = Mn; Z = Sn; x = 13, 14) were prepared by arc melting followed by thermal treatment. Structural properties were analyzed with X‐ray diffraction at room temperature (RT) and at elevated temperatures, above the martensite—austenite transition area, to determine the relevant crystallographic parameters and observe the transition. Martensite stabilization at RT appears to be a challenge, coexistence of martensite—austenite phases were observed and calculated for both 38–12 and 39–11 (16% and 12% austenite, respectively). Magnetization measurements versus temperature and field were recorded in the areas of interest where 1st order transitions were expected (355 K for x = 13 and 408 K for x = 14), and the magnetic entropy's changes (ΔSm) were determined [0.4 (J/kgK) for x = 13 and 0.3 J/(kgK) for x = 14; Hmax = 1 T]. The complex character of the magnetic properties and their dependence on Mn‐Sn ratio and on the distance between Mn atoms is discussed. The structure and the lattice parameters were determined using an anisotropic strain broadening model; stress and strain were detected in the structure due to crystal phase coexistence. [ABSTRACT FROM AUTHOR]

Abstract The structural stability, magneto-electronic, mechanical, thermodynamic, thermoelectric and optical, characteristics of the Hf2VZ (Z = Ga, In, Tl) Heusler alloy are revealed and understood by a comprehensive investigation employing density functional theory simulations. The stability of these alloys in F-43m phase is confirmed by structural optimizations and cohesive energies, which also provide the equilibrium lattice parameters. Compared to generalized gradient approximations, modified Becke–Johnson methods were more effective in determining the electrical structure and ground state attributes. Hf2VZ (Z = Ga, In, Tl) is predicted to have half-metallic ferromagnetic characteristics with indirect spin-up gaps based on the band structure analysis and density of state calculations. Stability of these compounds is determined by calculating the elastic constants indicating the ductile nature of these alloys. The quasi-harmonic Debye model is used to predict the effects of temperature and pressure on thermodynamic characteristics, conveying the alloys' thermodynamic stability. To estimate the thermoelectric performance of these materials, we compute electrical conductivities and Seebeck coefficients. The optical parameters like absorption coefficient, optical conductivity, dielectric constants etc., were determined to show the photo-voltaic applications of these alloys. Hence, the finding will lead to future research on developing new types of Hafnium based Heusler alloys for spintronics, thermoelectric and optoelectronics applications.

Theoretical and experimental approaches have been employed for studying the lattice site occupation effect on the electronic structure and some physical properties of CoMnCrAl Heusler alloy (HA). Among possible variants of the ordered stoichiometric CoMnCrAl HA lattice site occupation by Co, Mn, Cr, and Al atoms, the first-principle calculations have been performed for three nonequivalent ones (marked by us as type 1, type 2, and type 3, respectively). CoMnCrAl HA with atomic order of the first type is half-metallic ferromagnet (FM) with resulting magnetic moment of m t o t 1 = 0.9999 μ B /f.u. and spin-polarization degree of Fermi electrons P 1 = 100 % , for atomic orders of second and third types, m t o t and P are equal to m t o t 2 = 1.0186 μ B /f.u., P 2 = 89 % and m t o t 3 = 6.8673 μ B /f.u., P 3 = 77 % , respectively. Changes in the order type on the way T1 → T2 → T3 cause a decrease in the spatial electron density, weakening of the covalent chemical interatomic bonds, lead to a decrease in the cohesion energy E c o h and hence to loss of the thermodynamic stability of the CoMnCrAl alloy. Despite various high-temperature heat treatments, only B2- and A2-types of atomic order have been obtained in bulk and film CoMnCrAl alloy samples. Experimentally, it was found that bulk B2-type ordered CoMnCrAl alloy demonstrates significantly lower magnetization [ M (300 K) = 0.442 μ B /f.u.] and spin-polarization degree of Fermi electrons [ P ≈ 30 % ] than theoretically predicted. More disordered crystalline CoMnCrAl films with A2-type of atomic order practically are non-FM at T = 300 K with P = 0. [ABSTRACT FROM AUTHOR]

Obtaining Heusler alloys at the nanoscale with good crystallographic features is appealing for a large range of technological applications, from biomedical to spintronics devices. In particular, Fe 2 CrAl as bulk is known to present magnetic properties that are strongly sensitive to chemical and physical constraints, such as structural disorder and chemical composition. We report a throughout structural, morphological, and magnetic characterization of Fe 2 CrAl Heusler nanoparticles obtained by pulsed laser deposition technique. The nanoparticles are composed of slightly off-stoichiometric grains with two distinct morphologies where the role of chemical disorder and inhomogeneity on the magnetic behavior was evaluated. Through DC magnetization measurements, a superparamagnetic behavior is observed and a Gilbert damping of 9 × 10 − 3 is acquired from broadband ferromagnetic resonance data, which is comparable with standard materials used for magnonics applications. We discuss the complex magnetostructural coupling that rises on the nanoparticle system, comparing these results with the stoichiometric Fe 2 CrAl bulk target behavior. [ABSTRACT FROM AUTHOR]

Co2MnGe (CMG) has been demonstrated recently as a half-metallic ferromagnetic Heusler alloy, which possesses a topologically non-trivial band structure. This behavior is unique to such systems and hence warrants extensive experimental exploration for potential spintronic and chirality sensitive optoelectronic applications. Here, we demonstrate that an epitaxial thin film of CMG acts as a source of terahertz (THz) radiation upon photoexcitation by optical femtosecond laser pulses. Detailed experiments have revealed that a large contribution to THz emission occurs due to nonmagnetic or spin-independent origin; however, a significant contribution in the THz generation is evidenced through an excitation light helicity-dependent circular photogalvanic effect confirming the presence of topologically non-trivial carriers in the epitaxial CMG thin films. Furthermore, we show that not only the topological contribution is easily suppressed but also the overall THz generation efficiency is also affected adversely for the epitaxial films grown at high substrate temperatures. [ABSTRACT FROM AUTHOR]

In this study, we present results of a comprehensive computational and experimental study of CoFeVAl and CoFeV0.5Mn0.5Al Heusler alloys. It is shown that while CoFeVAl exhibits a fairly large degree of spin polarization, this material is not half-metallic due to the presence of the vanadium spin-down states at the Fermi level. However, replacing 50% of vanadium with manganese results in a nearly half-metallic transition, largely due to the shift of the Fermi level towards occupied states. Moreover, the half-metallicity of CoFeV0.5Mn0.5Al is rather robust in a wide range of considered mechanical strain and under experimentally observed B2-type atomic disorder, thus making this alloy potentially suitable for practical spintronic applications. Both considered alloys exhibit ferromagnetic alignment at larger lattice constants, aside from a relatively small magnetic moment of vanadium which is anti-aligned with the magnetic moments of Co, Fe and Mn. We have synthesized both CoFeVAl and CoFeV0.5Mn0.5Al alloys in cubic structure with some structural disorder using arc melting and annealing. The structural and magnetic properties of the synthesized CoFeV0.5Mn0.5Al alloy are in good agreement with the theoretical calculations but vary slightly from the parent compound. [ABSTRACT FROM AUTHOR]

Herein, a simple strategy for fabricating amorphous Co2FeGe nanoflakes by tuning the milling time with mechanical alloying method to enhance the microwave absorption capabilities is presented. These alloys exhibit soft magnetic properties characterized by high saturation magnetization and low coercivity. The enhancement of polarization and resonance effects, leading to improved magnetic and dielectric loss, is attributed to the refinement of crystalline size and the substantial aspect ratio of flaky particles. The minimum reflection loss reaches −48.6 dB at 4.92 GHz with an effective absorption bandwidth of 2.88 GHz in the C‐band. Due to its high Curie temperature, Co2FeGe exhibits considerable potential for maintaining highly efficient microwave absorption capabilities under high‐temperature conditions, thereby providing a novel perspective and technical means for the development of new high‐temperature‐resistant, high‐performance microwave‐absorbing materials. This is expected to play a significant role in future high‐temperature electronic countermeasure systems. [ABSTRACT FROM AUTHOR]

The structural, magnetoelectronic, mechanical, thermodynamical, thermoelectric, and optical properties of V2XSb (X = Mn, Fe) alloys are simulated using density functional theory. The structural optimization is done in Hg2CuTi prototype structure with F‐43m space group and confirms its stability in ferromagnetic state. The generalized gradient approximation and modified Becke–Johnson (mBJ) method are used to depict the half‐metallic nature of these alloys. Using Tran Blaha's mBJ potentials, the estimated indirect bandgap along the symmetry points is 0.54 eV for V2MnSb and 0.56 eV for V2FeSb. The total spin magnetic moments of V2XSb (X = Mn, Fe) are 3 and 2 μB which are in accordance with the Slater–Pauling rule. The mechanical stability reveal the ductile nature. The thermodynamic properties are calculated to determine the effect of temperature and pressure. The optical properties of these Heusler alloys are investigated to determine the absorbing power and optical conductivity. Using Boltzmann transport theory, thermoelectric parameters such as Seebeck coefficient and electrical conductivity are also depicted. The designated compound V2XSb (X = Mn, Fe) is unique due to the fact that that it has a high figure of merit (ZT) at both high and low temperatures, which is a beneficial parameter for converting squandered heat energy into beneficial energy that preserves the environment and is free of global warming and other hazardous substances. [ABSTRACT FROM AUTHOR]

The two-way shape memory effect with reversible compressive strain up to 5.1% and high cyclic stability is obtained for Ni44Fe19Ga27Co10 (at.%) single crystals by stress-induced martensite aging at 398 K for 1–3 h, under 650 MPa. 100 cycles of thermal treatment at temperatures not exceeding aging temperature, do not affect the temperature of the martensite formation, and reversible strain reduces merely by 0.4%. Thermal cycling with aging overheating significantly decreases reversible strain down to 1% due to the austenite stabilization. [ABSTRACT FROM AUTHOR]

In the present paper, we present an electron magnetic resonance (EMR) study of Ni 50.2 Mn 28.3 Ga 21.5 powders obtained from melt-spun ribbons in the milling process. We registered EMR spectra in various temperatures at the X-band. In the EMR spectra recorded for the samples taken at the beginning of the milling process, the "training effect" was observed. After 2 h of milling, this phenomenon was no longer observed. To determine the basic EMR parameters, such as linewidth, resonance field, and asymmetry parameters, the experimental data were fitted using a single metallic Lorentz line. In high-temperature regions, we observed the influence of dispersion on the shape of the spectra, but as the temperature decreased, the asymmetry of line was reduced. The shift in the resonance field value at high temperatures and the temperature dependence of the linewidth below Curie temperature indicate that the investigated samples exhibited a characteristics of a spin-glass alloy. [ABSTRACT FROM AUTHOR]

Fe50Mn35Sn15 Heusler alloy, obtained by mechanical alloying, was subjected to larger milling times in the range of 30–50 h to study the phase stability and morphology. X-ray diffraction studies have shown that the milled samples crystallise in a disordered A2 structure. The A2 structure was found to be stable in the milling range studied, contrary to the computation studies performed on this composition. Using Rietveld refinements, the lattice parameter, mean crystallite size, and lattice strain were computed. The nature of the obtained phases by milling was found to be nanocrystalline with values below 50 nm. A linear increase rate of 0.00713 (h−1) was computed for lattice strain as the milling time increased. As the milling time increases, the lattice parameter of the cubic Heusler was found to have a decreasing behaviour, reaching 2.9517 Å at 50 h of milling. The morphological and elemental distribution—characterised by scanning electron microscopy and energy-dispersive X-ray spectroscopy—evidenced Mn and Sn phase clustering. As the milling time increased, the morphology of the sample was found to change. The Mn and Sn cluster size was quantified by elemental line profile. Electrical resistivity evolution with milling time was analysed, showing a peak for 40 h of milling time. [ABSTRACT FROM AUTHOR]

Ternary half-Heusler (HH) alloys are under intense investigations recently towards achieving high thermoelectric (TE) figure-of-merit (ZT). Of particular interest is the ZrNiPb-based HH alloy, where an optimal value of ZT ~ 0.7 at 773 K has been achieved by co-doping Sn and Bi at Pb site. In this work, we identify an excellent ZT of 1.3 in ZrNi1+xPb0.38Sn0.6Bi0.02 (x = 0.03, at 773 K) composite alloy. This is achieved by synergistic modulation of electronic as well as thermal properties via introduction of minor phase of full-Heusler (FH) in the HH matrix through compositional tuning approach. These Ni-rich ZrNi1+xPb0.38Sn0.6Bi0.02 (0 ≤ x ≤ 0.07) alloys were synthesized via energy efficient and time-curbed techniques that involved Arc melting followed by consolidation via spark plasma sintering. These alloys were characterized by XRD and SEM, which show formation of nanocomposites comprising of HH matrix phase and FH secondary minor phases. Enhancement in ZT is mainly attributed to a synchronized increase in power factor (~42%) and ~25% decrease in its thermal conductivity. Here, TE compatibility factor (S) was also calculated for all samples. The value of |S| ~ 2.7 V−1 (at 773 K) is observed for x = 0.03, which is ~17% higher than bare HH composition (x = 0.0). The theoretically calculated TE device efficiency of best-performing sample ZrNi1.03Pb0.38Sn0.6Bi0.02 is estimated to be η ~ 13.6%. Our results imply that deliberately controlled fine tuning in compositions of HH compounds through compositional tuning approach would lead to novel off-stoichiometric HH phases with enhanced ZT value for efficient TE device fabrication. [ABSTRACT FROM AUTHOR]

In this paper, we present studies relating to the structural, electronic, magnetic and mechanical properties of TiHfFeX (X = Al , Ga, In) full Heusler alloys. We will use the GGA-PBE, TB-mBj, GGA-PBEsol, and GGA-WC approximation implemented in the density functional of the theory as integrated into the Wien2k software. However, the full Heusler alloys studied are considered in the ferromagnetic phase for different structural stabilities of the TiHfFeAl, TiHfFeGa and TiHfFeIn phases. types I, II or III, respectively. Calculation of band structures and total electron density of states shows that these alloys can both exhibit topologically non-trivial semi-metallic characteristics with energy bandgaps of 0.010 eV, 0.014 eV and 0.018 eV. The electronic stability of 'such a Heusler structure will have nothing to do with its mechanical stability. Calculations reveal that the systems exhibit semi-metallic ferromagnetism. The elastic constants and the associated elastic moduli confirm its stability given by different elastic constants namely the Cauchy pressure, Poisson's ratio, the anisotropy factor, Young's modulus and the shear modulus. [ABSTRACT FROM AUTHOR]

In this work, we have used the full-potential linearized augmented plane wave (FP-LAPW) method implemented in the WIEN2k code combined with the generalized gradient approximation (GGA) of the density functional theory (DFT) to study the structural, elastic, mechanical, electronic, magnetic, and thermodynamic properties of the parent ternary inverse Heusler compounds based on Titanium and Cobalt Ti2CoGa, Ti2CoCu in the Hg2CuTi-type structure and their quaternary alloys Ti2CoGa 1 − x Cux (x = 0. 2 5 , 0.5, 0.75) for the chosen concentrations using a supercell with 16 atoms. We have calculated the structural properties, such as the lattice parameters, bulk modulus, and its first derivative, which are in good agreement with those that have been obtained based on other published theoretical methods. Also, we calculated the elastic constants of the studied Heusler alloys, and we found that these materials are elastically stable, ductile, and anisotropic. Therefore, the electronic and magnetic properties indicate that Ti2CoGa exhibits a half-metallic (HM) ferromagnetic behavior, while Ti2CoCu shows a metal and a non-magnetic (NM) character. Their quaternary alloys are found to be nearly HM ferromagnetic materials, with a magnetic moment mainly due to the atom Ti. Furthermore, the quasi-harmonic Debye model, which incorporates the lattice vibrations, was used to estimate the thermodynamic effects on some macroproperties of the Ti2CoGa 1 − x Cux alloys. Successful results were achieved for the variations of the primitive cell volume, bulk modulus, heat capacities, and Debye temperature with pressure and temperature, respectively, in the ranges of 0–30 GPa and 0–1400 K. To our knowledge, no analogous investigations on the mechanical and thermodynamic properties of the Ti2CoGa 1 − x Cux (x = 0. 2 5 , 0.5 and 0.75) alloys have been performed to date. As a result, it is predicted that Ti2CoGa 1 − x Cux Heusler alloys will be promising candidates for actual applications in spintronic devices. [ABSTRACT FROM AUTHOR]

This research paper explores the structural, electronic, magnetic, elastic, dynamic, and thermoelectric properties of sp-based half-Heusler (HH) RbBaX (X = Si and Ge) compounds using density functional theory (DFT) and the full-potential linearized augmented plane wave (FP-LAPW) method within the WIEN2k software package. We evaluate the exchange correlation potential using two different approaches: The generalized gradient approximation (GGA) and the modified Becke–Johnson approach. We observe that RbBaX (X = Si and Ge) adopts a ferromagnetic configuration based on the analysis of total energy against volume. We establish that these alloys possess a genuine half-metallic character because of the full spin polarization observed at the Fermi level in their electronic spectrum. Both compounds under investigation have a total magnetic moment of 1.00 μ B, in agreement with the Slater–Pauling principle. The Born stability criteria for cubic structures and phonon dispersion patterns confirm the mechanical and dynamic stability of RbBaX (X = Si and Ge) alloys. The thermoelectric properties reveal a p-type semiconductor nature, characterized by significant positive Seebeck values. The thermoelectric figure of merit (ZT) calculated for both alloys at 300 K approaches unity, highlighting their remarkable thermoelectric efficiency. [ABSTRACT FROM AUTHOR]

Despite immense interest for years in Heusler alloys as magnetoelastic materials, their application in heterogeneous catalysis has only recently been explored. We report the development of highly active, robust and magnetically separable Ni2MnAl Heusler alloy nanoparticles as a heterogeneous catalyst for hydrogenation of aliphatic and aromatic nitro compounds to the corresponding amines. The easily synthesizable Ni2MnAl nanoparticles are thermally and chemically robust and exhibited excellent chemoselectivity in the hydrogenation of a range of aliphatic and aromatic nitroarenes, including those bearing functional groups sensitive to reduction, such as alkene, bromo, iodo, carbonyl and cyano, yielding the respective functionalized amines in good yields. Moreover, this solid catalyst is magnetically separable from the reaction mixture and could be recycled and reused at least 10 times without any loss in catalytic activity. The mechanism of the Ni2MnAl Heusler alloy nanoparticles catalyzed nitro reduction was studied by various spectroscopy, control experiments and kinetics. Our work opens a new avenue of developing heterogeneous earth‐abundant metal catalysis for economic and environment‐friendly synthesis of fine chemicals owing to straightforward synthesis and tunable composition of Heusler alloy nanoparticles from base‐metal precursors and their diverse structure and properties in conjunction with their thermal and chemical stability, excellent chemoselectivity, magnetic separability and recyclability. [ABSTRACT FROM AUTHOR]