Electronic correlations in short-period (CrAs)n/(GaAs)nferromagnetic heterostructures

Abstract

We investigate half-metallicity in [001] stacked (CrAs)n/(GaAs)n heterostructures with n ≤ 3 by means of a combined many-body and electronic structure calculation. Interface states in the presence of strong electronic correlations are discussed for the case n = 1. For n = 2, 3 our results indicate that the minority spin half-metallic gap is suppressed by local correlations at finite temperatures, and continuously shrinks upon increasing the heterostructure period. Although around room temperature the magnetization of the heterostructure deviates by only 2% from the ideal integer value, finite temperature polarization at EF is reduced by at least 25%. Below the Fermi level the minority spin highest valence states are found to localize more on the GaAs layers while lowest conduction states have a many-body origin. Our results, therefore, suggest that in these heterostructures holes and electrons remain separated among different layers.

Theoretical investigation of spin-filtering in CrAs/GaAs heterostructures

“…As a consequence, at the Fermi level, the polarization is significantly reduced, while dynamic correlations produce only a small deviation in magnetization. 29 Essentially, the same effect was found for defect-free digital magnetic heterostructures d-doped with Cr and Mn. 30 In addition, both studies indicate that the minority spin highest valence states below the Fermi level are localized more in the GaAs layers, while the lowest conduction band states have a many-body origin derived from CrAs.…”

“…The latter is important because theoretical studies have implied that the occurrence of half-metallicity in CrAs/GaAs superlattices is sensitive to layer thickness and lattice constant. 29 The ab-initio spin-dependent electronic band structures are mapped onto an ETB model, which is used to construct the effective Hamiltonian of the n-GaAs/CrAs/n-GaAs heterostructures consisting, respectively, of ' ¼ 4; 6; 8; 10 monolayers of CrAs. This down-folding was constrained by the requirement that As ETB onsite parameters for a given spin orientation be constant throughout the system, thereby, eliminating the need for the introduction of ad-hoc ETB parameters at the heterointerface.…”

“…In particular, the half-metallic behavior as a function of superlattice period and lattice constants has been investigated. 29,39 Details of this approach, as well as its benefits and caveats, can be found in the literature. 38 Our supercells, e.g., for (CrAs) 6 /(GaAs) 6 , extend along the [001] direction of the of bulk ZB material.…”

“…For a discussion of the latter, we refer to recent work. 29 In what follows we present results for the I-V characteristics of GaAs/(CrAs) ' /GaAs heterostructures for ' ¼ 4; 6; 8; 10. While thin layers of ZB CrAs may be easier to realize experimentally, thicker layers thereof are described more realistically within our approach.…”

Spin-polarized ballistic conduction through correlated Au-NiMnSb-Au heterostructures

“…The density of NQP states vanishes at E F at zero temperature and increases on the energy scale of the order of a characteristic magnon frequency [2,14,[73][74][75]. This has been calculated from first principles for semi-Heuslers [14,15], Heuslers [16,76], zinc-blend half-metals [55,77], and heterostructures [78,79].…”