Heusler interfaces—Opportunities beyond spintronics?

Abstract

Heusler compounds, in both cubic and hexagonal polymorphs, exhibit a remarkable range of electronic, magnetic, elastic, and topological properties, rivaling that of the transition metal oxides. To date, research on these quantum materials has focused primarily on bulk magnetic and thermoelectric properties or on applications in spintronics. More broadly, however, Heuslers provide a platform for discovery and manipulation of emergent properties at well-defined crystalline interfaces. Here, motivated by advances in the epitaxial growth of layered Heusler heterostructures, I present a vision for Heusler interfaces, focusing on the frontiers and challenges that lie beyond spintronics. The ability to grow these materials epitaxially on technologically important semiconductor substrates, such as GaAs, Ge, and Si, provides a direct path for their integration with modern electronics. Further advances will require new methods to control the stoichiometry and defects to "electronic grade" quality, and to control the interface abruptness and ordering at the atomic scale. arXiv:1908.00101v1 [cond-mat.mtrl-sci]

Electronic correlations in the semiconducting half-Heusler compound FeVSb

“…Density functional theory * jkawasaki@wisc.edu (DFT) calculations in the absence of on-site Coulomb repulsion predict a bandgap of 0.37 eV, larger than the ∼ 100 meV predicted for FeSi [15,16]. While FeVSb and other 18 electron half-Heuslers are promising materials for thermoelectric power conversion [17][18][19], Heusler compounds more broadly exhibit highly tunable topological states [20][21][22][23], magnetism [24][25][26], and novel superconductivity [27,28] as a function of electron count [29,30]. Here, using angle-resolved photoemission spectroscopy measurements, we reveal a mass enhancement of m * /m bare = 1.4 in epitaxial FeVSb films with respect to the DFT band mass m bare .…”

Understanding magnetic phase coexistence in Ru2Mn1−xFexSn Heusler alloys: A neutron scattering, thermodynamic, and phenomenological analysis

“…These alloys crystallize in cubic full-Heusler (X2YZ) and half-Heusler (XYZ) variants, incorporating a variety of X and Y transition metals (e.g., Mn, Fe, Co, Ru) and Z main group elements (e.g., Al, Si, Ga, Ge, In, Sn, Sb) [1,2]. Magnetic examples from this alloy class provide perfect illustrations of their diverse functionalities, which include: ferromagnetism with nonmagnetic X, Y, Z; high Curie temperature (TC) and saturation magnetization (MS); half-metallic or highly spin-polarized character; spin-gapless semiconducting behavior; magnetocaloric response; and exciting topological characteristics [1][2][3][4]. Particularly extensively studied in this context are NiMnSb and the Co2MnZ and Ni2MnZ families, although interest has been widespread [1][2][3][4].…”

“…Magnetic examples from this alloy class provide perfect illustrations of their diverse functionalities, which include: ferromagnetism with nonmagnetic X, Y, Z; high Curie temperature (TC) and saturation magnetization (MS); half-metallic or highly spin-polarized character; spin-gapless semiconducting behavior; magnetocaloric response; and exciting topological characteristics [1][2][3][4]. Particularly extensively studied in this context are NiMnSb and the Co2MnZ and Ni2MnZ families, although interest has been widespread [1][2][3][4]. A pervasive strategy in the investigation of such materials is to study quaternary solid solution or deliberately off-stoichiometric versions, such as Co2FeGe1-xGax, Ni2Mn1+xSn1-x, etc., which enable composition-based tuning of lattice parameter, spinpolarized electronic structure, topological band structure, and so on [1][2][3][4].…”

“…Particularly extensively studied in this context are NiMnSb and the Co2MnZ and Ni2MnZ families, although interest has been widespread [1][2][3][4]. A pervasive strategy in the investigation of such materials is to study quaternary solid solution or deliberately off-stoichiometric versions, such as Co2FeGe1-xGax, Ni2Mn1+xSn1-x, etc., which enable composition-based tuning of lattice parameter, spinpolarized electronic structure, topological band structure, and so on [1][2][3][4].…”

Semi-adsorption-controlled growth window for half Heusler FeVSb epitaxial films

“…However, it remains an outstanding challenge to control the stoichiometry to "electronicgrade" quality. For example, while the intrinsic carrier concentration of silicon is n i ∼ 10 10 cm −3 at room temperature, typical experimental carrier concentrations for semiconducting half Heuslers are typically ∼ 10 19 to 10 21 cm −3 due to defects and nonstoichiometry, which are difficult to control to better than 1% [21]. In select cases it has been shown that several Sb-containing Heuslersincluding CoTiSb [22,23], NiMnSb [24,25], LuPtSb [26], LaPtSb [27], and LaAuSb [28] -can be grown with an excess Sb flux, in which the ratio of Sb to (X + Y ) is self-limiting.…”