First-principles prediction of magnetically ordered half-metals above room temperature

Abstract

Half-metallicity (HM) offers great potential for engineering spintronic applications, yet only few magnetic materials present metallicity in just one spin channel. In addition, most HM systems become magnetically disordered at temperatures well below ambient conditions, which further hinders the development of spin-based electronic devices. Here, we use first-principles methods based on density functional theory (DFT) to investigate the electronic, magnetic, structural, mixing, and vibrational properties of 90 XY Z half-Heusler (HH) alloys (X = Li, Na, K, Rb, Cs; Y = V, Nb, Ta; Z = Si, Ge, Sn, S, Se, Te). We disclose a total of 28 new HH compounds that are ferromagnetic, vibrationally stable, and HM, with semiconductor band gaps in the range of 1-4 eV and HM band gaps of 0.2-0.8 eV. By performing Monte Carlo simulations of a spin Heisenberg model fitted to DFT energies, we estimate the Curie temperature, TC, of each HM compound. We find that 17 HH HM remain magnetically ordered at and above room temperature, namely, 300 ≤ TC ≤ 450 K, with total magnetic moments of 2 and 4 µB. A further materials sieve based on zero-temperature mixing energies let us to conclude 5 overall promising ferromagnetic HH HM at and above room temperature: NaVSi, RbVTe, CsVS, CsVSe, and RbNbTe. We also predict 2 ferromagnetic materials that are semiconductor and magnetically ordered at ambient conditions: LiVSi and LiVGe. arXiv:1812.04813v1 [cond-mat.mtrl-sci]

Tantalum half-Heusler alloys RbTaSi and RbTaGe: potential candidates for desirable thermoelectric and spintronic applications

“…The obtained values of band gaps are consistent with the reported values. 22 However, the bands at the Fermi level of spin up states do not shi, thereby validating the half-metallicity in these alloys.…”

“…Recently, half-Heusler compounds with 8 valence electrons, due to their compatible electronic structure and thermal stability, are regarded as prospective materials for spintronic applications. 22 Motivated by the aforementioned characteristics and multi-dimensional applications, cubic half-metallic RbTaZ (Z: Si, Ge) Heusler alloys have been selected in the present work. There are no detailed results regarding the mechanical characteristics, thermodynamic and transport properties of these alloys; therefore, our results would pose their future applications in energy harvesting and spintronic technologies.…”

High-throughput design of magnetic materials

“…Ma et al carried out HTP calculations on 378 half Heuslers and identified 26 semiconductors, 45 half metals, and 34 nearly half metals, which are thermodynamically stable [80]. Another recent work investigated the alkaline element based half Heuslers and found 28 FM materials out of 90 compositions [542]. Importantly, for half Heusler materials, it is not enough to consider only the binary competing phases, but also possible ternary compounds as there are many crystal structures which can be stabilized based on the 18-electron rule for the 1:1:1 composition [543].…”

Experimental and Theoretical Investigations of Fe-Doped Hexagonal MnNiGe

“…FM compounds with a large change in magnetic entropy and adiabatic temperature T ad (change in temperature of the system under adiabatic condition without exchange of heat) across the transition temperature near room temperature are potential candidates for technological applications such as magnetic refrigeration. In recent times, Heusler compounds have become materials of topical interest for their multifunctional and peculiar properties such as topological insulators, , Weyl semimetals, spin-gapless semiconductors, shape memory effect, , half-metals, − exchange bias, large magnetoresistance, and magnetocaloric effect. , …”