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The phase transitions of a series of Co-doped Heusler alloys, Ni 2 Mn 1 − x Co x Ga (0 ⩽ x ⩽ 0.2), were investigated experimentally using the magnetization measurements, x-ray diffraction, and calorimetric measurements up to their respective melting points. With increasing Co concentration, the structural transition temperatures, Curie temperatures, and melting points, were observed to increase, while the order–disorder transition temperatures decreased. Temperature-dependent x-ray diffraction experiments revealed two different crystal structures in the low-temperature martensite phase for different Co concentrations. However, above their respective structural transitions, both low-temperature crystal structures transformed into the L2 1 cubic structure. These findings enabled the construction of a complete magnetic and structural phase diagram for Ni 2 Mn 1 − x Co x Ga, spanning from cryogenic temperatures to the melting points. The temperature-dependent XRD results revealed the abrupt changes in interatomic Mn–Mn distances, which validates the crucial role of Mn–Mn interatomic distance and the effect of the magnetic coupling competition in the structural stability between the martensite phase and austenite phase. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of Co addition and atomic ordering on the magnetic and magnetocaloric properties of all-d-metal Heusler alloys Ni 2 − x Co x Mn 1.25 Ti 0.75 , which exhibit a second-order magnetic phase transition. The modeling approach employed is based on the density functional theory and Monte Carlo method. The atomic ordering is considered with reference to the fully ordered structure, L2 1 , and the partially ordered structure, B2. It is demonstrated that in both structures, the predominant magnetic state within the cubic austenitic phase is characterized by ferromagnetic ordering. An increase in the Co content results in the strengthening of the ferromagnetic exchange interactions between Mn, Ni, and Co, as well as an increase in the Curie temperature. For the ground state L2 1 structure, the largest Curie temperature values are observed, exceeding those of the B2 structure by almost 100 K. The temperature dependencies of the magnetization and magnetocaloric effect (Δ S m a g ) in magnetic fields up to 2 T are calculated using the Heisenberg Hamiltonian by the Monte Carlo method. The largest effect (Δ S m a g ≈ 1.4 J/kg K) is observed for the compound with x = 0.375 and B2 structure at temperature ≈ 150 K, whereas for L2 1 -Ni 1.5 Co 0.5 Mn 1.25 Ti 0.75 and B2-Ni 1.25 Co 0.75 Mn 1.25 Ti 0.75 , Δ S m a g of 1.05 J/kg K appears in the vicinity of room temperature. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of Co addition and atomic ordering on the magnetic and magnetocaloric properties of all-d-metal Heusler alloys Ni 2 − x Co x Mn 1.25 Ti 0.75 , which exhibit a second-order magnetic phase transition. The modeling approach employed is based on the density functional theory and Monte Carlo method. The atomic ordering is considered with reference to the fully ordered structure, L2 1 , and the partially ordered structure, B2. It is demonstrated that in both structures, the predominant magnetic state within the cubic austenitic phase is characterized by ferromagnetic ordering. An increase in the Co content results in the strengthening of the ferromagnetic exchange interactions between Mn, Ni, and Co, as well as an increase in the Curie temperature. For the ground state L2 1 structure, the largest Curie temperature values are observed, exceeding those of the B2 structure by almost 100 K. The temperature dependencies of the magnetization and magnetocaloric effect (Δ S m a g ) in magnetic fields up to 2 T are calculated using the Heisenberg Hamiltonian by the Monte Carlo method. The largest effect (Δ S m a g ≈ 1.4 J/kg K) is observed for the compound with x = 0.375 and B2 structure at temperature ≈ 150 K, whereas for L2 1 -Ni 1.5 Co 0.5 Mn 1.25 Ti 0.75 and B2-Ni 1.25 Co 0.75 Mn 1.25 Ti 0.75 , Δ S m a g of 1.05 J/kg K appears in the vicinity of room temperature. [ABSTRACT FROM AUTHOR]

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]

The physical properties of Ni2XAl (X = V, Fe) alloys were investigated using the full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT), employing the Wien2K code. The generalized gradient approximation (GGA) was applied for the exchange and correlation potential (XC) during structural optimization. The elastic analysis indicates that both Ni2VAl and Ni2FeAl alloys are mechanically stable. Ni2FeAl is a spin-magnetic alloy that crystallizes in a stable cubic structure, while Ni2VAl is a non-magnetic alloy with a stable L21 cubic structure. Our study reveals that Ni2VAl exhibits metallic characteristics in its electronic properties, and similarly, Ni2FeAl demonstrates metallic behavior in both spin-up and spin-down states. Regarding magnetism, Ni2VAl is non-magnetic, in contrast to the magnetic Ni2FeAl. These findings suggest that Ni2XAl (X = V, Fe) alloys are promising candidates for future applications in spintronics. [ABSTRACT FROM AUTHOR]

First principles investigations have been carried out for half-Heusler alloys MnCrX (X = P, As, Sb). The electronic band structures and density of states are computed for under study alloys. Reststrahlen bands are explained through the phonon dispersion curve calculated using Quantum ESPRESSO. The positive phonon frequencies in full zone ascertain the dynamic stability of all these under-study alloys. MnCrP exhibits a larger value of the Reststrahlen band than the other two and is an important candidate in Far Infra-Red spectroscopy applications. Moreover, the thermoelectric coefficients as a function of temperature have been studied using the Boltzmann transport equation. Half Heusler alloys have not yet explored for these properties. The power factor of MnCrP is the highest amongst these studied materials. [ABSTRACT FROM AUTHOR]

In this paper, we have studied the structural, mechanical, electronic, magnetic and thermodynamical properties of the Heusler alloys CoNbTiX ( X = A l , G a , I n ). We used full potential linearized augmented plane wave method based on density functional theory. We analysed and compared the various properties using both GGA and TB-mBJ XC functionals. Our analysis shows that among all the Y1, Y2 and Y3-type structures, Y1-structure is more stable and having ferromagnetic property. Also, the mechanical property analysis reveals that all the alloys are ductile in nature. The density of states of Heusler alloys CoNbTiX ( X = A l , G a , I n ) shows that in all the alloys the spin up channel having metallic and spin down channel having semi-conducting property. All the Heusler alloys under investigation having the integer spin magnetic moment and the values are concurrence with the Slater - Pauling rule. The thermodynamic properties of the Heusler alloys CoNbTiX ( X = A l , G a , I n ) like specific heat capacity, thermal expansion, Debye temperature, vibrational free energy, internal energy and entropy are studied using quasi-harmonic approximation. [ABSTRACT FROM AUTHOR]

In this work, we will investigate structural, electronic, magnetic, and thermodynamic properties using density functional theory (DFT) and the quasi-harmonic Debye model. We consider ferromagnetic (FM) and non-magnetic (NM) states for L21 and Hg2CuTi-type crystal structures. The best stability is obtained for ferromagnetic Rh2MnGa in a Cu2MnAl structure with a lattice parameter of 6.07 Å and a total magnetic moment of 4.11 μB. The compressive strain range from −6% to +4% tensile strain maintains the ferromagnetic nature and enhances the magnetic moment up to 4.39 μB. The formation energy confirms the inherent stability of Rh2MnGa. Other important thermodynamic parameters such as the expansion coefficient (α), heat capacity (CV), Debye temperature (θD) and Grüneisen constant (γ) are also estimated in this work. [ABSTRACT FROM AUTHOR]

Manganese-based alloys with the composition Mn2FeZ (Z = Si, Al) have been extensively investigated in recent years due to their potential applications in spintronics. The Mn2FeSi alloy, prepared in the form of ingots, powders, or ribbons, exhibits either a cubic full-Heusler (L21) structure, an inverse-Heusler (XA) structure, or a combination of both. In contrast, the Mn2FeAl alloy has so far been synthesized only in the form of ingots, featuring a primitive cubic (β-Mn type) structure. This study focuses on the new quaternary Mn2FeSi0.5Al0.5 alloy synthesized from pure Mn, Fe, Si, and Al powders via mechanical alloying. The elemental powders were ball-milled for 168 h with a ball-to-powder ratio of 10:1, followed by annealing at 550 °C, 700 °C, and 950 °C for 8 h in an argon protective atmosphere. The results demonstrate that annealing at lower temperatures (550 °C) led to the formation of a Heusler structure with a lattice constant of 0.5739 nm. Annealing at 700 °C resulted in the coexistence of several phases, including the Heusler phase and a newly developed primitive cubic β-Mn structure. Further increasing the annealing temperature to 950 °C completely suppressed the Heusler phase, with the β-Mn structure, having a lattice constant of 0.6281 nm, becoming the dominant phase. These findings confirm the possibility of tuning the structure of Mn2FeSi0.5Al0.5 alloy powder—and thereby its physical properties—by varying the annealing temperature. The sensitivity of magnetic properties to structural changes is demonstrated through magnetization curves and zero-field-cooled/field-cooled curves in the temperature range of 5 K to 300 K. [ABSTRACT FROM AUTHOR]

This study examines the structural stability, electronic, and magnetic properties of off-stoichiometric Zn2Ru1−xAxMn Heusler alloys (with, A = Ti, Mn, Co, Zr, and Rh) using first-principles calculations. We find that the L 2 1 phase is more stable than the XA phase across both ordered and disordered configurations. The variations in lattice parameters with off-stoichiometry are attributed to the atomic radii of the dopants. Our results indicate that Zn2Ru1−xAxMn alloys exhibit ferromagnetic metallic behavior, driven primarily by Mn-Mn, Ru-Mn, and A-Mn exchange interactions. These interactions are further analyzed to calculate the Curie temperature using the mean-field approximation. The Curie temperature for Zn2RuMn is found to be approximately 300 K, which increases to 428 K upon Co doping. Our findings suggest that doping provides a means to control the Curie temperature, offering substantial potential for applications in room-temperature magnetocaloric materials and shape memory alloys. This tunability enhances the functional versatility of these alloys, making them promising candidates for future technological applications. [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]

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]

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]

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]

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]

The synthesis of polycrystalline TiFe2Sn samples by a route including arc melting and spark plasma sintering with Hf, Y, and In substitutions at the Ti and Sn sites is investigated. For a reduced amount of substitution, around 2 at%, the samples are single phase, while for increased amounts, secondary phases segregate. As is characteristic of these compounds, the Fe-Ti atomic disorder generates a weak ferromagnetic ordering, which is also influenced by the type of substitutional atoms and the secondary phases in the samples with a higher Hf content. The Seebeck coefficient values show an increase for Ti0.98Hf0.02Fe2Sn and for samples with an adjusted Sn content, resulting in slightly increased power factor values. These values reach a maximum for Ti0.98Hf0.02Fe2Sn at approximately 300 K and for TiFe2Sn1.05 at approximately 325 K, namely, 2.69 × 10⁻4 Wm−1K−2 and 2.52 × 10⁻4 Wm−1K−2, respectively. The thermal conductivity of all the samples with substitutions increases with respect to the pristine sample. The highest figure of merit value of 0.016 is also obtained for Ti0.98Hf0.02Fe2Sn at 325 K. [ABSTRACT FROM AUTHOR]

Heusler alloys (HAs) are a well‐known family of compounds generating promising interest due to their robust structure, ease of tailoring their unique properties, and potential applications. The investigations in the direction of the electrochemical performance of these materials as electrodes for rechargeable lithium‐ion batteries (LIBs) have been established theoretically and experimentally. Alloying of alkali metal ions into half‐HAs unit cells can be another route to improve LIBs performance. This work presents our investigations on thermodynamically stable half‐HAs CoMnZ (Z: Sb/Sn) as electrode materials for rechargeable LIBs using the first‐principle calculations based on the density functional theory. The negative formation energies validate the thermodynamic stability of the alloys considered in this study. With increasing Li doping, a structural change from cubic to tetragonal and orthorhombic phase is observed in the host structure, and upon full lithiation (LiMnZ), a cubic structure is attained. The band structure calculations of the host structure and its lithiated phase indicate a metallic nature in these alloys. The calculations are also performed to investigate the structural stability of parent alloys and corresponding lithiated phases. We calculated a storage capacity of around 14.5 Ah/kg for 0.125 atomic fraction of Li atoms, which is increased by nearly 10 times upon full lithiation. A maximum open circuit voltage of around 9.8 V is calculated for Li0.125Co0.875MnSb and CoLi0.125Mn0.875Sb. Thus, all these remarkable results suggest that these intermetallic compounds have a strong potential as the cathode material for LIBs with a robust life and a large capacity. [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]