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A comprehensive investigation is conducted on the electronic structure and magnetic properties of half‐Heusler NaScGe, which is doped with a rare earth element Nd with different concentrations. The Heusler Na1‐xNdxScGe (where x = 0, 0.25, 0.75, and 1) compounds are thoroughly investigated. The examination encompassed structural, elastic, magnetic, and electronic characteristics using the full potential linearized augmented plane wave (FP‐LAPW) method. Generalized gradient approximation (GGA) is used to calculate the structural parameters and electronic characteristics. The equilibrium lattice constant and band gap of half‐Heusler NaScGe are found to be in good accord with other data. The density of states (DOS) investigation has revealed a semiconductor behavior of half‐Heusler NaScGe and half‐metallic ferromagnetic properties of quaternary‐Heusler Na0.75Nd0.25ScGe, characterized by a moderate band gap in minority spin channel. In addition, the DOS analysis has shown that both ternary half‐Heusler NdScGe and QH Na0.25Nd0.75ScGe compounds have exhibited metallic ferromagnetic activity. The work has introduced a novel approach for producing half metals from the semiconductor half‐Heusler NaScGe. Quaternary‐Heusler Na0.75Nd0.25ScGe is identified as a promising material for applications spintronic. [ABSTRACT FROM AUTHOR]

This work concerns innovative approach to prepare Pb–Sn–Ba grids for lead-acid batteries which provides their enhanced structural stability and mechanical properties allowing functionality and prolongation of service life at high temperatures. To have these properties in the Pb–Sn–Ba grids, two roll melt spinning technology is applied that provides a greater to extreme environments resistance to fatigue, higher mechanical properties, thermal (for high temperature exposure) stability. As a result, far less disposal and environmental hazard will be posed by longer-lived lead-acid batteries with the Pb–Sn–Ba grids prepared using melt spinning technology compared to those fabricated by conventional methods. [ABSTRACT FROM AUTHOR]

Double perovskite materials are particularly well suited for energy applications because of their nontoxic, efficient, and environmentally advantageous characteristics. Using the full-potential linearized augmented-plane-wave approach, Ba2DyTaO6 oxide double perovskite was thoroughly examined to investigate the microstructural, magnetic, and optoelectronic properties. The thermodynamic and structural stability was mapped by computing the phonon properties, tolerance factor, and octahedral factor, respectively, which revealed that Ba2DyTaO6 was highly stable. The results were determined based on the electronic and magnetic properties obtained from the data. The band edges at the same symmetry points indicated that there was a direct bandgap in the (ΓV–ΓC) direction in the majority spin, a value equal to 3.793 eV with an overlap in the minority spin. With an integer magnetic moment value of 5.00 μB, the Ba2DyTaO6 compound exhibits half-metallic and ferromagnetic behavior. This research is the first of its kind in terms of optical properties. It can be concluded that the Ba2DyTaO6 material has high absorption, and can be applied in future optoelectronic applications throughout a wide energy range of the light spectrum. Given the limited availability of theoretical and experimental data, the present investigation can provide value for future studies on this compound. Our findings can thus pave the way for additional investigations into the potential use of this oxide material in numerous chemical and physical applications intended for socioeconomic needs. [ABSTRACT FROM AUTHOR]

Heusler alloy is a ferromagnetic alloy based on the Heusler phase. It is an intermetallic alloy between metallic and non-metallic elements that can be non-ferromagnetic and has a BCC crystal structure. This paper presents the theory of thermodynamics and elastic deformation of full-Heusler A2BC alloy with BCC structure built on the basis of statistical moment method (SMM). The paper presents numerical results for the temperature and pressure dependence of the mean nearest neighbor distance between two atoms, the density, the volume, the thermal expansion coefficient, the isotherm and adiabatic compressibilities, the isothermal elastic modulus, the heat capacities at constant volume and pressure, Young's modulus, the bulk modulus, longitudinal and transverse wave velocities of alloys Co2TaGa and Co2VGa when using the coordination sphere method and the Mie–Lennard-Jones pair interaction potential. Some SMM calculation results agree well with available ab initio calculation results. [ABSTRACT FROM AUTHOR]

This document is an editorial from the journal "Metals" titled "Crystallography and Applications of Metallic Materials." It discusses the scientific and technological interest in metals and metallic alloys, highlighting their wide range of applications in fields such as mobility, biomedicine, heat transfer, energy, and sustainability. The special issue aims to present the current knowledge and trends in metallic materials based on crystallography development and analysis, focusing on the relationships between microstructure, properties, and applications. The document provides a summary of the contributions made by various manuscripts, covering topics such as crystal orientation, dislocation slip, phase transformations, corrosion behavior, nucleation, additive manufacturing, and magnetic properties. The editorial concludes by emphasizing the value of understanding the processing-microstructure-property relationships in the development and design of new metallic materials. [Extracted from the article]

The structural, dynamical, electrical, magnetic, and thermoelectric properties of CoMRhSi (M = Cr, Mn) quaternary Heusler alloys (QHAs) were investigated using density functional theory (DFT). The Y-type-II crystal structure was found to be the most stable configuration for these QHAs. Both CoCrRhSi and CoMnRhSi alloys possess a half-metallic behavior with a 100% spin-polarization as the majority spin channel is metallic. On the other hand, the minority spin channel is semiconducting with narrow indirect band gaps of 0.54 eV and 0.57 eV, respectively, along the Γ − X high symmetry line. In addition, both CoCrRhSi and CoMnRhSi alloys possess a ferromagnetic structure with total magnetic moments of 4 μB, and 5 μB, respectively, which are prominent for spintronics applications. The thermoelectric properties of the subject QHAs were calculated by using Boltzmann transport theory within the constant relaxation time approximation. The lattice thermal conductivities were also evaluated by Slack's equation. The predicted values of the figure-of-merit (ZT) for CoCrRhSi and CoMnRhSi were found to be 0.84 and 2.04 at 800 K, respectively, making them ideal candidates for thermoelectric applications. [ABSTRACT FROM AUTHOR]

A Ni2MnSn Heusler alloy was obtained as a single B2 phase after 12 h of mechanical milling. The influence of prolonged milling on the phase stability was analysed for milling times up to 50 h, related to mean crystallite size, lattice strain, and electrical resistivity. The nature of the powders in the milled range was found to be nanocrystalline, with a mean crystallite size of about 33 ± 2 nm. An evaluation of the internal stresses induced by milling was performed, a linear behaviour was found, and a coefficient of the internal stress increase with milling time was proposed. Particle size distributions of milled samples were analysed, and the morphology of the powders was visualised by scanning electron microscopy. The elemental distribution of milled samples was quantified by energy-dispersive X-ray spectroscopy. Electrical resistivity measurements were performed on compacted samples, and their behaviour with milling time was analysed.

Solitonic magnetic excitations such as domain walls and, specifically, skyrmionics enable the possibility of compact, high density, ultrafast, all-electronic, low-energy devices, which is the basis for the emerging area of skyrmionics. The topological winding of skyrmion spins affects their overall lifetime, energetics, and dynamical behavior. In this Perspective, we discuss skyrmionics in the context of the present-day solid-state memory landscape and show how their size, stability, and mobility can be controlled by material engineering, as well as how they can be nucleated and detected. Ferrimagnets near their compensation points are promising candidates for this application, leading to a detailed exploration of amorphous CoGd as well as the study of emergent materials such as Mn 4 N and inverse Heusler alloys. Along with material properties, geometrical parameters such as film thickness, defect density, and notches can be used to tune skyrmion properties, such as their size and stability. Topology, however, can be a double-edged sword, especially for isolated metastable skyrmions, as it brings stability at the cost of additional damping and deflective Magnus forces compared to domain walls. Skyrmion deformation in response to forces also makes them intrinsically slower than domain walls. We explore potential analog applications of skyrmions, including temporal memory at low density—one skyrmion per racetrack—that capitalizes on their near ballistic current–velocity relation to map temporal data to spatial data and decorrelators for stochastic computing at a higher density that capitalizes on their interactions. We summarize the main challenges of achieving a skyrmionics technology, including maintaining positional stability with very high accuracy and electrical readout, especially for small ferrimagnetic skyrmions, deterministic nucleation, and annihilation and overall integration with digital circuits with the associated circuit overhead. [ABSTRACT FROM AUTHOR]

Based on the first principles of the generalized gradient approximation method, the magnetic and optical properties of Fe-, Ni-doped and (Fe,Ni) co-doped LiNbO 3 crystals are studied. The results show that the mono-doped LiNbO 3 crystals contain magnetic atoms (Fe,Ni) leading to spin polarization, and (Fe,Ni) co-doped LiNbO 3 crystals tend to the ferromagnetic state with △ E F M of − 143 meV. The total magnetic moment of the (Fe,Ni) co-doped LiNbO 3 crystal is 5.97 μ B , and the local magnetic moments of Fe and Ni are 2.99 μ B and 0.93 μ B , respectively. It is interesting that the introduction of the Ga atom makes the ferromagnetic state (△ E F M of − 285.4 meV) of the (Fe,Ni) co-doped LiNbO 3 system more stable than the anti-ferromagnetic state. Although Ga atoms do not contribute to the magnetic moment, the (Fe,Ni,Ga) co-doped LiNbO 3 is more conducive to the spin-polarized state. In addition, with the introduction of Fe, Ni, and Ga atoms, the visible region absorption changes significantly. Non-volatile holographic storage can be achieved by (Fe,Ni) co-doped LiNbO 3 , thus increasing the absorption of the visible light range. In summary, this research provides theoretical guidance for the application of LiNbO 3 crystals in spintronic devices. [ABSTRACT FROM AUTHOR]

As for spintronic applications, all information is encoded in the spin degree of freedom, so the key issues are the high spin-polarization, large half-metallic (HM) bandgap, large magnetic moment and higher Curie temperature than room temperature. In this paper, we studied halogen based CsYZ2 (Y = V or Cr; Z = F, Cl, Br or I) full-Heusler alloys. Our study reveals that CsVF2, CsVCl2, CsVI2 and CsCrI2 alloys are all HM ferromagnets while remaining alloys exhibits magnetic semiconductor behavior. The electronic structures indicate that these alloys open very large bandgaps in the spin-down channel. Following the Slater-Pauling rule Mt=Zt-16, these alloys exhibit very large total magnetic moments Mt of 4.00 μBf.u. when Y = V and 5.00 μBf.u. when Y = Cr. The high Curie temperatures indicate these alloys are appropriate for spintronic applications at room temperature. Furthermore, the absorption coefficient α(ω) of the CsVF2 alloy is better from other alloys in the visible region. The maximum ZT = 0.7 is obtained for CsCrBr2 and is an ideal candidate for thermoelectric (TE) applications.

This paper contains data and results from Density Functional Theory (DFT) investigation of 423 distinct X2YZ ternary full Heusler alloys, where X and Y represent elements from the D-block of the periodic table and Z signifies element from main group. The study encompasses both “regular” and “inverse” Heusler phases of these alloys for a total of 846 potential materials. For each specific alloy and each phase, a range of information is provided including total energy, formation energy, lattice constant, total and site-specific magnetic moments, spin polarization as well as total and projected density of electronic states. The aim of creating this dataset is to provide fundamental theoretical insights into ternary X2YZ Heusler alloys for further theoretical and experimental analysis.

Light transition metals have recently emerged as a sustainable material class for efficient spin–charge interconversion. We report measurements of current-induced spin–orbit torques generated by Ni1−xCux alloys in perpendicularly magnetized ferrimagnetic Gd/Fe multilayers. We show that the spin–orbit torque efficiency of Ni1−xCux increases with the Ni/Cu atomic ratio, reaching values comparable to those of Pt for Ni55Cu45. Furthermore, we demonstrate magnetization switching of a 20-nm-thick Gd/Fe multilayer with a threshold current that decreases with increasing Ni concentration, similar to the spin–orbit torque efficiency. Our findings show that Ni1−x Cu x − based magnetic heterostructures allow for efficient control of the magnetization by electric currents. [ABSTRACT FROM AUTHOR]

By using density functional theory, we have explored the structural, electro-mechanical, thermophysical and thermoelectric properties of CoZrSi and CoZrGe Heusler alloys. The ground state stability was determined by optimising the energy in various configurations like type I, II, and III. It was found that these alloys stabilized in the ferromagnetic phase in type I. We employed the Generalised Gradient Approximation and modified Becke-Johnson potentials to explore the electronic structure. The band structures of each of these Heusler alloys exhibit a half-metallic nature. Additionally, the computed second-order elastic parameters reveal their ductile nature of them. To understand the stability of the alloys at different pressures and temperatures, we investigated various thermodynamic parameters using the Quasi-Harmonic Debye model. We obtained the transport coefficients using the Boltzmann theory. Our findings indicate that these alloys can be used in spintronics and thermoelectric domains. [ABSTRACT FROM AUTHOR]

Magnetic shape memory alloys exhibit various multifunctional properties, which range from high stroke actuation and magnetocaloric refrigeration to thermomagnetic energy harvesting. Most of these applications benefit from miniaturization and a single crystalline state. Epitaxial film growth is so far only possible on some oxidic substrates, but they are expensive and incompatible with standard microsystem technologies. Here, epitaxial growth of Ni–Mn–based Heusler alloys with single crystal‐like properties on silicon substrates is demonstrated by using a SrTiO3 buffer. It is shown that this allows using standard microfabrication technologies to prepare partly freestanding patterns. This approach is versatile, as its applicability for the NiTi shape memory alloy is demonstrated and spintronic and thermoelectric Heusler alloys are discussed. This paves the way for integrating additional multifunctional effects into state‐of‐the‐art microelectronic and micromechanical technology, which is based on silicon. [ABSTRACT FROM AUTHOR]

In this study, we investigate the effects of doping with ∼10 at% of Si, Al, Sn, and Bi on the atomic order, microstructure, and magnetic properties of CoMnSb samples prepared using the arc-melting method. X-ray diffraction, scanning electron microscopy, and magnetometry techniques were employed to derive the structural and magnetic parameters. The samples demonstrate a superstructure with an Fm -3 m space group. They exhibit a saturation moment of 3.71–4.71 μ B per formula unit at 5 K and a Curie temperature ranging from 474 to 507 K. Rietveld refinement performed on the XRD data revealed a possible occupation of magnetic atoms in the vacant 32 f (x ', x ', x ') sites and atomic swapping, both of which may affect the magnitudes of the magnetic moment and Curie temperature. The electrical measurement results show that the grain boundaries and voids govern the conductivity of the samples. The spin polarization of the Si-doped sample was determined based on the grain-boundary magnetoresistance effect, which showed that this sample has a high degree of atomic order, consistent with the low magnetic moment, Curie temperature, and lattice constant. [ABSTRACT FROM AUTHOR]

The inherent high thermal conductivity of TiNiSn half-Heusler (HH) alloy, as well as the long preparation cycle time and high cost of conventional preparation methods limited its commercial application. Herein, Ti1 – xNbxNiSn half-Heusler alloys with low lattice thermal conductivity were successfully prepared by microwave synthesis combined with rapid hot-pressing sintering, which significantly shortened the preparation cycle and ensured high density of TiNiSn half-Heusler alloys. The effects of Nb substitution at Ti sites on the composition distribution, thermal and electrical transport properties of Ti1 – xNbxNiSn half-Heusler samples were studied. The maximum ZT value of Ti0.9Nb0.1NiSn sample was 0.39 at 725 K due to the increase of power factor (PF) and the decrease of lattice thermal conductivity caused by the enhanced phonon scattering, which was about 204% higher than that of undoped TiNiSn. [ABSTRACT FROM AUTHOR]

Ni50 − x Mn37 + x Sb13 (NMS (x = 4–6)) melt-spun Heusler ribbon was fabricated by employing the arc melting technique. Also, the electrical, structural, and magnetic characteristics of melt-spun alloy ribbons with chemically increased Mn (a decrease in Ni concentration) content are also being investigated. Further, it has been noticed that, the Curie temperatures of the austenitic (T CA) phase and the martensitic phase transition temperature (T M) are both shifted toward higher temperatures, by increasing the amount of Mn under 500 Oe (0.05 T) of applied magnetic fields. The discontinuity of field cooling (FC) and zero field cooling (ZFC) curves reveals the irreversibility of magnetization caused by inhomogeneous magnetic anisotropy lower the exchange bias (EB) (blocking bias) temperature. Furthermore, the disappearance of exchange bias (EB) in ribbon alloys with increasing temperature is supported by the fact that coercivity (H C) gradually increases with temperature and increases at 40 K, and then decreases with temperature. Additionally, a −Δ S Max of −5.21 Jkg−1·K−1 for a ribbon with x = 6 is acquired at 312 K with a 50 kOe (5 T) change in the applied magnetic field. Increases in Mn content result in −Δ S M values in NMS alloy ribbons of −4.3, −4.7, and −5.2 Jkg−1·K−1 and the same trend is observed in negative magneto-resistance ((−MR) (%)) values of −9%, −11%, and −14% for x = 4–6, respectively. Here, the super zone boundary that is close to the Fermi surface is responsible for the change in −MR. [ABSTRACT FROM AUTHOR]

The exchange bias effect is the physical cornerstone of applications, such as spin valves, ultra-high-density data storage, and magnetic tunnel junctions. This work studied the room temperature exchange bias effect by constructing a Ni50Mn38Sb12−xGax alloy system with coexisting martensitic phase structures. The study found that the exchange bias effect shows a non-monotonic change with the variation of Ga composition at 300 K, and an obvious room temperature exchange bias effect appears in the alloys with coexisting phase structures of 4O and L10, which is due to the strong exchange coupling between ferromagnetic and antiferromagnetic. Further research on the exchange bias effect and temperature shows that the blocking temperature is 420 K, and the exchange bias can stably exist in a temperature range of ∼200 K around room temperature. This work provides a method to engineer exchange bias effects at room temperature. [ABSTRACT FROM AUTHOR]

Heusler alloys constitute an interesting group of materials with wide applications. The purpose of the present study was to use the mechanical alloying method to synthesize Fe2CrSi Heusler alloy and learn about its structure and magnetic properties. Pure metal elements were ground for various periods of time in a planetary ball mill, and the process of alloy formation was monitored using X-ray diffraction and Mössbauer spectroscopy. It was found that after 20 h of milling, the disordered BCC solid solution was formed, with an average crystallite size ~11 nm. After thermal treatment, the desired Fe2CrSi Heusler alloy was obtained, with a small amount of secondary phases. Detailed XRD analysis showed the coexistence of two varieties of Heusler phase, namely Fm-3m and Pm-3n. The main result of this work is the detection of the hyperfine magnetic field distribution using Mössbauer spectroscopy. The occurrence of this distribution proves atomic disorder in the crystalline structure of the obtained Heusler alloy. Macroscopic magnetic measurements revealed soft magnetic properties of the alloy, with a magnetic moment of ~2.3 μB/f.u., only slightly larger than the theoretically predicted value. [ABSTRACT FROM AUTHOR]

The study focuses on investigating the half-metallic ferromagnetic (HMF) behavior in 4d transition metal (TM)–doped MgSe with a zinc-blende crystal structure. The calculations are performed using ab initio methods based on the KKR-CPA (Korringa-Kohn-Rostoker Coherent Potential Approximation) approach. Findings include lattice parameters, band structure, total and partial densities of states, magnetic moment, and Curie temperature of D-doped MgSe where D = Y, Zr, Nb, and Mo. The results show that all impurities except Y atoms added a magnetic moment to the systems. We also obtained a half-metallic character for Nb and Mo doping of MgSe. The most stable phase of magnetic compounds is the ferromagnetic phase, with a high Curie temperature (it reached 700 K). The results obtained from these calculations will provide insights into the half-metallic ferromagnetic (HMF) character, such as the presence of a band gap in one-spin channel and metallic behavior in the other, which makes this MgSe-based DMS a promising candidate for spintronics applications. [ABSTRACT FROM AUTHOR]

We predict a series of XYZ-type half-Heusler RuMnZ (Z = Si, Ge, Sn, P, As, Sb, Se, and Te) alloys, using density functional theory (DFT) calculations. Structural, electronic structure, magnetic moments, and elastic properties are carried out using both GGA and GGA+U approximations to determine the viability of this series of alloys for spintronic applications. The band structure (BS) and density of states (DOS) calculations are carried out to explain the half-metallic and magnetic nature of the predicted alloys. RuMnZ alloys stabilize to the F 4 ¯ 3 m space group with a ferrimagnetic (FiM) ground state, with the exception of RuMnSn, which has a ferromagnetic (FM) ground state. Interestingly, RuMnP/As/Te alloys exhibit half-metallic properties with 100% spin polarization at the Fermi level among the predicted alloys. When U is included in the calculations (GGA+U), the half-metallicity is completely lifted. Further, upon incorporating pressure under GGA+U, a band gap is induced again, and the half-metallicity in RuMnTe is robust up to a compressive pressure of 140 GPa. Calculation of the elastic properties shows that RuMnZ has a ductile nature. [ABSTRACT FROM AUTHOR]

In the present work, we study the geometric, electronic, magnetic and mechanical properties of Co-based full Heusler alloys Co2TaZ (where Z = Si and Sn). Structural optimization and physical properties have been investigated using density functional theory (DFT) calculations. While calculating electronic and magnetic properties, the GGA+U scheme, where U is the Hubbard term, predicts more efficient results than the generalized gradient approximation (GGA). The calculated electronic band structure and density of states (DOS) with spin magnetic moment reveal the half-metallic character of both alloys. The total computed magnetic moment amounts to a nearly integral value of 3 μB for Co2TaSi and Co2TaSn. It has been found that these alloys obey the Slater–Pauling rule. The calculated values of elastic constants indicate that these alloys are mechanically stable, difficult to compress and ductile. The high spin polarization at the Fermi level in these alloys makes them useful for spintronic applications. [ABSTRACT FROM AUTHOR]

Compton profiles (CPs) of TM2O3 (TM = Ti, V and Cr) have been measured using 100 mCi 241Am Compton spectrometer. The experimental momentum densities have been used to check the applicability of exchange-correlation energies using pure and hybrid density functional theory (DFT). Present ab-initio computations have been accomplished using the texture of Gaussian orbitals within linear combination of atomic orbitals (LCAO) scheme. Based on experimental and theoretical CPs, hybrid DFT schemes namely B3LYP and PBESOL0 have shown better performance than pure DFT (within local density and generalized gradient approximation), whereas the best agreement (through χ2 fitting of goodness) is obtained for B3LYP prescriptions. Besides Compton spectroscopy, the spin-up (↑) energy bands and density of states (DOS) have confirmed the metallic nature of all three compounds, whereas the spin-down (↓) energy bands and DOS for Ti2O3 and V2O3 have shown a peculiar semiconducting behaviour leading to their very peculiar half-metallic character. Further, higher values of charge transfer from all the 3d transition elements to O atoms, as witnessed using Mulliken's population analysis, show a dominancy of ionic nature in these oxides. Equally normalized CPs of these oxides show that the 3d electrons in oxide environment are delocalized (in real space) in the ascending sequence Cr→V→Ti, which is in contrast to their elemental-free atom environment. [ABSTRACT FROM AUTHOR]

Direct measurements of the magnetocaloric effect were performed in a Heusler Ni44.4Mn36.2Sn14.9Cu4.5 alloy at cryogenic temperatures in magnetic fields up to 10 T. The maximum value of the inverse magnetocaloric effect in a 10 T field was ∆Tad = –2.7 K in the vicinity of the first-order magnetostructural phase transition at T0 = 117 K. Ab initio and Monte Carlo calculations were performed to discuss the effect of Cu doping into a Ni-Mn-Sn compound on the ground-state structural and magnetic properties. It is shown that with increasing Cu content the martensitic transition temperature decreases and the Curie temperature of austenite slightly increases. In general, the calculated transition temperatures and magnetization values correlated well with the experimental ones. [ABSTRACT FROM AUTHOR]

The structural, magnetocaloric, and magnetic characteristics in Heusler Ni50Mn35In10X5 (X = Ga, Fe, and Al) alloys were examined using X-ray diffraction and field-dependent magnetization measurements. All samples exhibited a mixture structure of cubic L21 and tetragonal L10 and underwent second-order magnetic transitions at TC(Al5) = 220 K, TC(Ga5) = 252 K, and TC(Fe5) = 298 K. The Ga5 alloy exhibited structural change as indicated by a thermal hysteresis that may be seen in the saturation magnetic field in the M(T) dependences. The transition at the TC point from a ferromagnetic to a paramagnetic state caused a drop in magnetization, supported by thermal hysteresis, at a low magnetic field (0.01 T). On the other hand, the Fe5 alloy presented a gradual decrease in magnetization with similar hysteresis behavior, also at a low magnetic field (0.01 T), whereas at 0.1 T of field, no features characteristic of this transition were detected. This could be due to a large difference in the metallic radius of Fe compared to that of In. Otherwise, magnetic investigations demonstrated that the replacement of In with Al may cause the structural transformation temperatures and TC to be shifted to low temperatures. The present results imply that the structural transformation temperatures and the transition itself are highly dependent on chemical composition. Furthermore, under a magnetic field change of 5 T, the maximum magnetic entropy changes of 0.6 J/kg K, 1.4 J/kg K, and 2.71 J/kg K for the Ga5, Fe5, and Al5 alloys, respectively, were determined by their TC. Refrigeration capacity values were found to be 25 J/kg, 74 J/kg, and 98 J/kg at µ0∆H = 5 T. These ribbons are viable candidates for multifunctional applications due to their cheaper cost and their physical characteristics disclosed during the magnetostructural transition, which takes place close to the room temperature. [ABSTRACT FROM AUTHOR]

The thermoelectric figure-of-merit (zT) of p-type MNiSn (M = Ti, Zr, or Hf) half-Heusler compounds is lower than their η-type counterparts due to the presence of a donor in-gap state caused by Ni occupying tetrahedral interstitials. While ZrNiSn and TiNiSn, have been extensively studied, HfNiSn remains unexplored. Herein, this study reports an improved thermoelectric property in p-type HfNi1-xCoxSn. By doping 5 at% Co at the Ni sites, the Seebeck coefficient becomes reaching a peak value exceeding 200 μV K-1 that breaks the record of previous reports. A maximum power factor of ≈2.2 mW m-1 K-2 at 973 K is achieved by optimizing the carrier concentration. The enhanced p-type transport is ascribed to the reduced content of Ni defects, supported by first principle calculations and diffraction pattern refinement. Concomitantly, Co doping also softens the lattice and scatters phonons, resulting in a minimum lattice thermal conductivity of ≈1.8 W m-1 K-1. This leads to a peak zT of 0.55 at 973 K is realized, surpassing the best performing p-type MNiSn by 100%. This approach offers a new method to manipulate the intrinsic atomic disorder in half-Heusler materials, facilitating further optimization of their electronic and thermal properties. [ABSTRACT FROM AUTHOR]

We present a comprehensive investigation of the electromagnetic properties of CdAB2 compounds, where A represents Cr, Mn, or Fe, and B denotes P or As. To investigate the spin-polarized behavior of these compounds the A atoms were substituted at the Group IV (Ge) position in CdGeB2 in the chalcopyrite crystal structure. Our results reveal that all the CdAB2 compounds exhibit compelling spin-splitting of energy states near the Fermi level (EF). Notably, CdAB2 materials with A = Cr and Mn exhibit intriguing half-metallic ferromagnetic (HMF) characteristics, with the calculated total magnetic moments of 2.00 and 3.00 µB/f.u., respectively. The HMF properties originated in CdAB2 (A = Cr and Mn; B = P, As) these compounds owing to the hybridization of partially filled -3d(t2g) states of A atoms with the p-states of B (P, As) atoms, with minor contributions from Cd's-like states. In contrast, CdFeB2 displays distinct behavior, demonstrating spin-splitting of energy levels around the EF indicative of a stable ferromagnetic (FM) state and the absence of HMF at their equilibrium volume. The calculated total magnetic moments for CdFeP2 and CdFeAs2 are about 1.83 (1.64 µB/f.u.) and 1.94 µB/f.u. (1.84 µB/f.u.) under generalized gradient approximation (GGA) (local spin density approximation (LSDA)) approximations, respectively. Perhaps these CdAB2 compounds (A = Cr and Mn; B = P, As) with HMF characteristic within both LSDA and GGA formalisms makes them highly promising candidates for spin injectors in the spintronic device applications. Furthermore, their semiconducting nature renders CdCrB2 and CdMnB2 materials compatible with silicon and other semiconducting lattices, enhancing their potential practical applications in the spintronic technologies. In conclusion, this study presents a thorough exploration of the robust electronic and magnetic properties of CdAB2 chalcopyrites, offering exciting prospects for their utilization in the future spintronic applications. [ABSTRACT FROM AUTHOR]

The structural stability, optoelectronic and magnetic characteristics of K2NaMI6 (M = Mn, Co, and Ni) halide double perovskites have been demonstrated to be explained using density functional theory computations. The prominent generalized gradient approximation and integration of the mBJ potential are implemented to estimate the exchange–correlation potential, which is the only unidentified parameter in the state-of-the-art formulism. The structural optimization, mechanical stability criteria, and tolerance factor demonstrate the reliability of the double perovskites in a cubic structure with Fm3m symmetry. The elastic constants facilitated mechanical stability and revealed the brittle nature of these double perovskites. The spin-polarized electronic band profile and the behaviour of the dielectric constant and absorption coefficient in the spin-up and down channels show the presence of half-metallic nature in these materials. Additionally, we examined magnetism and the genesis of the half-metallic gap in this article. The half-metallic and magnetic properties are attributed to the unpaired electrons in the split d-orbitals of the M-sited elements in the crystal field. The Mn-, Co-, and Ni-based double perovskites were found to possess total magnetic moments of 4 μB, 4 μB, and 1 μB, respectively, with the transition metal atoms comprising up the majority of this magnetic moment. The Fermi level's perfect spin polarisation promotes the potential application of double perovskites in spintronic technology. [ABSTRACT FROM AUTHOR]

The perpendicular magnetocrystalline anisotropy, magnetoelastic properties as well as the Gilbert damping factor in Co2Fe0.4Mn0.6Si thin films were found to depend on a magnetic layer thickness, and they can be also tuned by the application of additional Ag buffer layer. The tetragonal distortion of a magnetic layer was found to increase with decreasing thickness, and after the application of an additional Ag buffer layer, the character of this distortion was changed from tensile to compressive in the plane of a film. A correlation between the tetragonal distortion and perpendicular magnetocrystalline anisotropy was found. However, the magnitude of the observed tetragonal distortion for most samples seems to be too small to explain alone the experimentally found large magnitude of the perpendicular magnetocrystalline anisotropy. For these samples, other mechanisms including both surface and volume effects must be taken into account. [ABSTRACT FROM AUTHOR]

The first-principles calculations have been employed to explore structural, electronic, magnetooptical and thermodynamic properties of Half-Heusler compounds XNiSb (X = Er, Ho, Yb). The FP-LAPW technique is executed using the WIEN2K package to simulate stable electronic, structural, magnetooptical and thermodynamics properties of studied half-Heusler compounds. The electronic properties (DOS and energy band structures) have been elucidated, considering the strong correlation between the d/f-states of Ni/X-atoms. It is evident from the presented GGA and GGA + U results that XNiSb (X = Er, Ho, Yb) show metallic nature; however, mBJ + U results show that these compounds are intermetallic. The ε 2 (ω) spectra reveal that XNiSb (X = Er, Ho, Yb) absorb a significant number of incident photons over a broad spectrum (∼1.0 to ∼6.0 eV). These compounds are weak reflectors of incident photons and reflect ∼40% of incident photons on the entire energy range. ErNiSb/HoNiSb show significant values of magnetic moments due to the splitting of [ 4 f 12 ] /[ 4 f 11 ] localized orbitals and are promising candidates for prospective spintronic applications. The elucidated thermodynamic characteristics reveal that these compounds are thermally stable. [ABSTRACT FROM AUTHOR]

Magnetic shape memory alloys are emerging multifunctional materials that enable applications like high-stroke actuation, solid-state refrigeration, and energy harvesting of waste heat. Thin films of these alloys promise integration in microsystems to exploit their multifunctional properties at the microscale. However, the microfabrication process of these Heusler alloys is difficult. Herein, different etching techniques are investigated for the microfabrication of epitaxial Ni-Mn-Ga films, the encountered challenges are explained, and ways to overcome them are demonstrated. The results show that wet chemical etching is suitable for large patterned structures, while reactive ion etching of Ni-Mn-Ga films is unsuitable due to redeposition. For patterning structures below 10 μm with clean and sharp edges, the best results are obtained by ion beam etching with adjusted sample-stage tilt. Finally, a microfabrication process using Si microtechnology to fabricate partially freestanding structures is demonstrated. These findings give guidelines for the fabrication and integration of these smart materials in Si-based microsystems. [ABSTRACT FROM AUTHOR]

Direct studies of the adiabatic temperature change (ΔTad) in the Ni47Mn40Sn12.5Cu0.5 Heusler alloy in steady magnetic fields up to 8 T by the extraction method and in pulsed magnetic fields up to 50 T were carried out in this paper. The alloy Ni47Mn40Sn12.5Cu0.5 demonstrates a magnetostructural phase transition (MSPT) of the first order in the 254–283 K temperature range as well as a second order phase transition near the Curie temperature TC = 313 K. An inverse magnetocaloric effect (MCE) was found in the region of the MSPT, and it reaches the maximum value ΔTad = −12 K in 20 T at the initial temperature T0 = 275 K. The irreversible part of the MCE reached ΔTir = −10 K when the field is completely removed. We consider the dynamics of the MCE in the vicinity of the MSPT and discuss the mechanisms that cause the giant irreversibility of the MCE as well as the possibilities of its application in hybrid cooling systems. [ABSTRACT FROM AUTHOR]

A full-potential linear augmented plane wave (FP-LAPW) has been used to study the structural, electronic, and optical properties of double half-Heusler alloys X2FeY′Sb2 with X≡Zr, Hf and Y′≡Pd, Ni. Electronic band structures and densities of states calculations of the four studied double half-Heusler alloys indicate that they are semiconductors with an indirect gap. The optical spectra of dielectric constants, refractive indices, reflectivity, and light absorption are also discussed. In the energy range of 8–14 eV, the calculated optical properties and mainly the absorption spectrum show very high UV absorption. Additionally, DFT calculations were combined with Boltzmann transport theory to estimate the thermoelectric properties, such as the thermal and electrical conductivity, Seebeck coefficient, and figure of merit (ZT), versus the change of temperature and chemical potential. These alloys possess a suitable band gap for diverse optoelectronic applications, encompassing photovoltaics, UV sensors, and solar cells. [ABSTRACT FROM AUTHOR]

Ab initio calculations have been conducted on all‐d light transition metals featuring full and inverse Heusler structures with the composition Ni2XMn, where X = Fe, Co, Cr. The analysis encompasses lattice parameters, bulk modulus, and formation energy, which are thoroughly examined across various magnetic orders. Additionally, the equilibrium structures are comprehensively characterized. Elastic constants are calculated and mechanical stability is thoroughly discussed. Furthermore, tetragonal distortions, following the Bain path, are computed, and a novel stable structure is introduced. Spin‐resolved density of electronic states and band structures are scrutinized in detail. The findings reveal a behavior consistent with half‐metallicity, even though the gaps between the conduction and valence bands are exceedingly small. [ABSTRACT FROM AUTHOR]

The structure of a material is an important factor in determining its physical properties. Here, we adjust the structure of the Ni50Mn37Ga13 spun ribbons by changing the wheel speed to regulate the exchange bias effect of the material. The characterization results of micromorphology and structure show that as the wheel speed increases, the martensite lath decreases from 200 nm to 50 nm, the structure changed from the NM to a NM and 10M mixed martensitic structure containing mainly NM, then changed to NM and 10M where 10M and NM are approaching. Meanwhile, HE first increased and then decreased as the wheel speed increased. The optimum exchange bias effect (HE = 7.2 kOe) occurs when the wheel speed is 25 m∙s−1, mainly attributed to the enhanced ferromagnetism caused by part of 10M in NM martensite, which enhanced the exchange coupling of ferromagnetism and antiferromagnetism. This work reveals the structural dependence of exchange bias and provides a way to tune the magnitude of the exchange bias of Heusler alloys. [ABSTRACT FROM AUTHOR]

The half-Heusler LiZnX (X = As, P, and Sb) alloys have gained a significant attention due to their exceptional thermoelectric and magnetic properties, making them a promising material for various applications. In this study, we employ density functional theory to investigate the data on structural and thermodynamics properties of the LiZnX (X = As, P, and Sb) half-Heusler alloys. First-principles calculations as implemented in quantum Espresso simulation software were used. We observed that LiZnX (X = As, P, and Sb) will be easily compressed due to the small value of its bulk modulus. We obtained that the structure is stable and corresponds a half-Heusler crystal one. The Debye model correctly predicts the observed low-temperature dependence of heat capacity, which is proportional to the Debye T3 law. At room temperature, Debye specific heat Cv = 70 J / (K⋅N⋅mol). [ABSTRACT FROM AUTHOR]

In this paper, the effect of heat treatment on the structure and magnetic properties of the alloy is investigated by heat treating the melted Fe2Cr1-xMnxGa samples at different temperatures. It is found that the structure and magnetic properties of Fe2Cr1-xMnxGa are very sensitive to heat treatment and there is a certain degree of disorder. The structure of the prepared samples changes with different conditions of heat treatment, and the change in structure will in turn affect the magnetic behavior of the alloy. The magnetization intensity increases with increasing annealing temperature, indicating that the orderliness of the samples is improved by heat treatment. The magnetization intensity of the samples decreases with the doping of Mn content, which is due to the anti-parallel arrangement of the Fe-Mn spin magnetic moments by the doped Mn atoms. [ABSTRACT FROM AUTHOR]

In this work, the structural, electronic, elastic, optical, and magnetic properties for the B1, B2, and B3 phases of Sr0.875Mn0.125O with relaxed structure (RS) and unrelaxed structure (URS) are investigated. The investigations are accomplished by the adoption of first‐principle methods established on spin‐polarized density functional theory, based on the full‐potential linearized augmented plane wave method as implemented in the WIEN2k code, where the electronic exchange‐correlation potential is studied by the Perdew–Burke–Ernzerhof generalized gradient approximation (GGA‐PBEsol) and the revised TB‐mBJ rapprochement. The negative formation energy and elastic constant that are acquired indicate the thermodynamical and mechanical stability of all these structures. The ternary Sr0.875Mn0.125O alloys for all structures show half‐metallic ferromagnetic behavior with a spin polarization of 100 % at the Fermi level, except the B2 phase without unrelaxed structure (URS). The total magnetic moments are 5 µB for all compounds and the interaction is ferromagnetic between Mn─Sr and Mn─O sites. Optical properties such as refractive index and the optical reflectivity for these alloys are computed and discussed. These materials are half‐metallic ferromagnets, and they can be desirable applicants for spintronics implementations and ultraviolet spectra. [ABSTRACT FROM AUTHOR]

Heusler alloys (X2YZ) can be a candidate for new catalysts as well as other intermetallic compounds. We previously found good catalytic properties of Co2FeGe for selective hydrogenation of alkynes and developed nanoparticles of Co2FeGe supported on SiO2. However, the average diameter of the nanoparticles was 23 nm, which is not small enough compared to those of state‐of‐the‐art nanoparticle catalysts. In this study, we developed SiO2‐supported Co2FeGe nanoparticles of <10 nm in diameter. A catalytic test for selective hydrogenation of propyne indicated a partial formation of sites with low selectivity including excess Co atoms. For ammonia decomposition, enhancement of turnover frequency was achieved by reducing the particle size. [ABSTRACT FROM AUTHOR]

The structural, electronic, mechanical and magnetic properties were investigated for Cr2LuSn1−xPbx quaternary Heusler compounds by employing first-principles calculations framed fundamentally within density functional theory. The exchange–correlation potential is evaluated using the generalized gradient approximation (GGA)within the Perdew–Burke–Ernzerhof parameterization. We optimized our structure, and the most stable crystal structure is AlCu2Mnl-type, and at equilibrium, equilibrium lattice parameters have been determined. The calculated lattice constants for Cr2LuSn and Cr2LuPb are 6.5906 Å and 6.6769 Å, respectively. The electronic structures show that both compounds have half-metallic properties by showing 100% spin polarization near the Fermi level. The electronic band structures and density of states of our compounds show a half metallic character with total magnetic moments, 5.00 μ b per formula unit with indirect band gap, 0.527 eV and 0.300 eV for Cr2LuSn and Cr2LuPb, respectively. The mechanical stability reveals that all our compounds are stable mechanically. The Young's modulus, Poisson's ratio, anisotropy factor Zener and density were calculated and discussed in detail. Furthermore, the temperature and pressure effect on bulk modulus, Debye temperature and heat capacity at constant volume and constant pressure C v , , respectively, have been investigated by the quasi-harmonic Debye model. These alloys seem to be a potential candidate of spintronic devices. [ABSTRACT FROM AUTHOR]

Samples of composites with different porosity and surface roughness based on LaFe11.4Mn0.3Si1.3H1.6 (LFMSH) alloy powders were obtained, their magnetocaloric properties were studied by the direct method in cyclic magnetic fields of μ0H = 1.2 T with a frequency of 2 Hz. The maximal value of the adiabatic temperature change in pure LFMSH powder was ΔT = 3 K at T0 = 287 K in the sample cooling regime, and for composite samples, this value was approximately two times lower than that in the powder. The effect of Mn and H atoms on the electronic structure and local magnetic characteristics of the initial La(Fe,Si)13 alloy was studied using electron density functional theory. Replacement of some Fe atoms with Mn reduces the total magnetic moment and somewhat lowers the Curie temperature. In contrast, hydrogenation leads to an increase in exchange interactions between Fe atoms located at the vertices of the icosahedron and an increase in the Curie temperature. [ABSTRACT FROM AUTHOR]

First-principles studies on phase stability and resistance with respect to the segregation of austenitic and martensitic phases of Ni2 – xCoxMn1 + yZ1 – y Heusler alloys (x = 0, 0.25, 0.5 and y = 0, 0.25, 0.5, 0.75; Z = Ga, In, Sb, Sn) with different types of magnetic ordering. Among all the considered compounds, the stability has been demonstrated only by the Ni1.5Co0.5MnGa and Ni2MnGa alloys in the cubic and tetragonal structures having a ferromagnetic ordering, respectively, as well as by Ni2Mn2 in the tetragonal structure with a staggered and layer-by-layer AFM ordering. For the case of these compositions, the presence of zero energy of the convex hull, as well as the absence of reactions with positive decomposition energy has been shown. The remaining compounds appear to be metastable, both owing to the presence of stable reactions with negative decomposition energy, and decomposition reactions with positive decomposition energy. The number of decomposition reactions exhibits an increase with increasing chemical disorder, i.e., with deviations from stoichiometry. [ABSTRACT FROM AUTHOR]

The results of the study of the influence of multi-axial isothermal forging on the microstructure and martensitic transformation in a Ni58Mn18Ga24 alloy have been presented. Forging is performed in two stages: the first stage is forging at 700°C by four passes with true strain e ≈ 1.64; the second stage is forging at 500°C by one pass with e ≈ 0.24. The forging deformation results in the transformation of the original equiaxed-grain structure. No new grains are formed after the first stage of treatment. New recrystallized grains in a very negligible extent begin to be observed only after the second stage of deformation. Probably, at the first stage, the mechanism of fragmentation of the grain structure is not started due to an insufficient density of defects upon the deformation at 700°C. The characteristic temperatures of martensitic transformation are shifted after forging to the low temperature region. The anharmonic change in the sample length is observed in the region of martensitic transformation for the both treated states. In general, this indicates a low level of defect density and internal stresses in the sample. [ABSTRACT FROM AUTHOR]

This study explores the impact of Cu and Zn atoms' alloying on the magnetic and structural features of cubic and tetragonal phase of the Ni2Mn1.125Ga0.875 Heusler alloy, using density functional theory. The partial substitution of Ga atoms by Cu and Zn atoms results in a reduction of energy difference between ferromagnetic and ferrimagnetic states of cubic phase, and in an elevation of the energy barrier between cubic and tetragonal phase. The latter observation indirectly implies that there has been a rise in the temperature of the structural transition that was experimentally observed. Within the scope of calculations of exchange interaction parameters from first principles and Monte Carlo simulations of temperature dependences of magnetization, a Т–х phase diagram was constructed. It has been demonstrated that the Curie temperature of the tetragonal phase exhibits a significant reduction compared to that of the cubic phase with an increase in Cu and Zn content due to the growth in inter-sublattice antiferromagnetic interaction between Mn atoms. [ABSTRACT FROM AUTHOR]

Abstract—Magnetic properties and electronic structure inherent in FeRhSn1 − xZx alloys (x = 0, 0.25, 0.5, 0.75, 1) have been studied with the use of first-principles methods in an environment of a VASP software package. It is shown that the γ-phase is energetically favorable in the case of all the alloys, except for the FeRhSi alloy, for which the β-phase is the equilibrium one. It has been shown that the addition of a fourth element to a three-component alloy leads to a change in the position of the valence band and conduction band with respect to the Fermi level, which makes it possible to obtain novel four-component alloys exhibiting an entirely overwhelming spin polarization. It is shown that the FeRhSn1 − xGex alloy (x = 0, 0.25, 0.5, 0.75, 1), FeRhSn1 − xSix alloy (x = 0, 0.25, 0.5, 0.75), and FeRhSn1 − xSbx alloy (x = 0, 0.25) represent halfmetallic ferromagnets. [ABSTRACT FROM AUTHOR]

We studied Ni2FeSi-, Co2FeSi-, and Co2MnSi-based full-Heusler alloy glass-coated microwires with the same geometric parameters, i.e., fixed nucleus and total diameters, prepared using the Taylor–Ulitovsky method. The fabrication of X2YZ (X = Co and Ni, Y = Fe and Mn, and Z = Si)-based glass-coated microwires with fixed geometric parameters is quite challenging due to the different sample preparation conditions. The XRD analysis showed a nanocrystalline microstructure for all the samples. The space groups Fm3¯m (FCC) and Im3¯m (BCC) with disordered B2 and A2 types are observed for Ni2FeSi and Co2FeSi, respectively. Meanwhile, a well-defined, ordered L21 type was observed for Co2MnSi GCMWs. The change in the positions of Ni, Co and Mn, Fe in X2YSi resulted in a variation in the lattice cell parameters and average grain size of the sample. The room-temperature magnetic behavior showed a dramatic change depending on the chemical composition, where Ni2FeSi MWs showed the highest coercivity (Hc) compared to Co2FeSi and Co2MnSi MWs. The Hc value of Ni2FeSi MWs was 16 times higher than that of Co2MnSi MWs and 3 times higher than that of Co2FeSi MWs. Meanwhile, the highest reduced remanence was reported for Co2FeSi MWs (Mr = 0.92), being about 0.82 and 0.22 for Ni2FeSi and Co2MnSi MWs, respectively. From the analysis of the temperature dependence of the magnetic properties (Hc and Mr) of X2YZ MWs, we deduced that the Hc showed a stable tendency for Co2MnSi and Co2FeSi MWs. Meanwhile, two flipped points were observed for Ni2FeSi MWs, where the behavior of Hc changed with temperature. For Mr, a monotonic increase on decreasing the temperature was observed for Co2FeSi and Ni2FeSi MWs, and it remained roughly stable for Co2MnSi MWs. The thermomagnetic curves at low magnetic field showed irreversible magnetic behavior for Co2MnSi and Co2FeSi MWs and regular ferromagnetic behavior for Ni2FeSi MWs. The current result illustrates the ability to tailor the structure and magnetic behavior of X2YZ MWs at fixed geometric parameters. Additionally, a different behavior was revealed in X2YZ MWs depending on the degree of ordering and element distribution. The tunability of the magnetic properties of X2YZ MWs makes them suitable for sensing applications. [ABSTRACT FROM AUTHOR]

Searching for an appropriate anode material with desirable electrochemical performance is crucial in the development of metal ion batteries. In this work, based on the extensive first‐principles computations, we have systemically assessed the potential of an emerging PN2 monolayer as an anode material for lithium (LIBs), sodium (NIBs) and potassium (KIBs) ion batteries. The PN2 monolayer possesses excellent thermal, dynamical and mechanical stability, and it is half‐metallic with two energy bands crossing over the Fermi level in the spin‐down channel. Moreover, the diffusion barriers of Li, Na and K atoms on the PN2 are as low as 0.11, 0.09 and 0.05 eV, showing a high ionic mobility. The storage capacities of PN2 anode are predicted to be 2725.53, 1413.24, and 908.51 mAh/g for LIBs, NIBs and KIBs. Importantly, the PN2 anode exhibits strong affinity towards metal atoms and negligible structural distortion during the whole intercalation process, which is of importance to improve the cyclability and prevent the metallic dendrite formation. All the encouraging findings demonstrate that the PN2 anode holds great promise in the high‐performance metal ion battery application. [ABSTRACT FROM AUTHOR]

The discovery of topological insulators and semimetals triggered enormous interest in exploring emergent electromagnetic responses in solids. Particular attention has been focused on ternary half-Heusler compounds, whose electronic structure bears analogy to the topological zinc-blende compounds while also including magnetic rare-earth ions coupled to conduction electrons. However, most of the research in this system has been in band-inverted zero-gap semiconductors such as GdPtBi, which still does not fully exhaust the large potential of this material class. Here, we report a less-studied member of half-Heusler compounds, HoAuSn, which we show is a trivial semimetal or narrow-gap semiconductor at zero magnetic field but undergoes a field-induced transition to a Weyl semimetal, with a negative magnetoresistance exceeding four orders of magnitude at low temperatures. The combined study of Shubnikov-de Haas oscillations and first-principles calculation suggests that the exchange field from Ho 4f moments reconstructs the band structure to induce Weyl points which play a key role in the strong suppression of large-angle carrier scattering. Our findings demonstrate the unique mechanism of colossal negative magnetoresistance and provide pathways towards realizing topological electronic states in a large class of magnetic half-Heusler compounds. Half-Heusler alloys containing rare earth ions have attracted interest due to combination of band-inversion and magnetism. Ueda et al study less studied trivial semiconductor HoAuSn, and show that it undergoes a magnetic field induced transition to a Weyl semimetal state, with a large reduction in the resistance. [ABSTRACT FROM AUTHOR]