Spin polarization at the NiMnSb/MgO(100) interface

Sicot, Muriel; Turban, Pascal; Andrieu, S.; Tagliaferri, Alberto; Nadaï, C. De; Brookes, N. B.; Bertran, F.; Fortuna, F.

doi:10.1016/j.jmmm.2005.10.229

Cited by 21 publications

(11 citation statements)

References 28 publications

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“…The possibility to tune the spin-polarization at E F both with CMS stoichiometry and MgO covering is a very promising result. It contrasts withthe NiMnSb Half-Heusler alloy case, for which the spin polarization is destroyed whenMgOis deposited on the surface [Sic06]. Altogether, these experiments are a strong indication that A and B contributions are probably similar bands originating from the surface andseparate in energy by exchange splitting of the electronic states due to the ferromagnetic behavior.…”

Section: Figure 1: (A) Full Density Of States For Both Spins Calculat...mentioning

confidence: 76%

Direct evidence for minority spin gap in theCo2MnSiHeusler compound

et al. 2016

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Half Metal Magnets are of great interest in the field of spintronics because of their potential full spin-polarization at the Fermi level and low magnetization damping. The high Curie temperature and predicted 0.7eV minority spin gap make the Heusler alloy Co 2 MnSi very promising for applications.We investigated the half-metallic magnetic character of this alloy using spin-resolved photoemission, ab initio calculation and ferromagnetic resonance. At the surface of Co 2 MnSi, a gap in the minority spin channel is observed, leading to 100%spin polarization. However, this gap is 0.3 eV below the Fermi level and a minority spin state is observed at the Fermi level. We showthat a minority spin gap at the Fermi energy can neverthelessbe recovered either by changing the stoichiometry of the alloy or by covering the surface byMn, MnSi or MgO. This results in extremely small damping coefficients reachingvalues as low as7x 10 -4 .

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Section: Figure 1: (A) Full Density Of States For Both Spins Calculat...mentioning

confidence: 76%

Direct evidence for minority spin gap in theCo2MnSiHeusler compound

et al. 2016

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“…Spin polarized photoemission spectroscopy (SPPES) can, in principle, measure P DOS more directly but it is strongly affected by the magnetic, chemical and structural conditions of the surface, which may differ from those of the bulk. Threshold SPPES measured P DOS ≤ 50% at T = 20K [5], while more recent works measured 40% [6] or 50% at T = 10K falling to 40% at T = 300K [7]. Inverse SPPES experiments implied similar P DOS values, again more dependent on surface condition than T [8].…”

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confidence: 76%

Cubic MnSb: Epitaxial growth of a predicted room temperature half-metal

et al. 2012

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Epitaxial films including bulk-like cubic and wurtzite polymorphs of MnSb have been grown by molecular beam epitaxy on GaAs via careful control of the Sb4/Mn flux ratio. Nonzero-temperature density functional theory was used to predict ab initio the spin polarization as a function of reduced magnetization for the half-metals NiMnSb and cubic MnSb. In both cases, half-metallicity is lost at a threshold magnetization reduction, corresponding to a temperature T * < TC . This threshold is far higher for cubic MnSb compared to NiMnSb and corresponds to T * > 350K, making epitaxial cubic MnSb a promising candidate for room temperature spin injection into semiconductors.Efficient electrical spin injection is crucial for the development of semiconductor (SC) spintronics, in which spin-polarized charge carriers flow from a ferromagnetic (FM) material into a non-magnetic SC structure. An ideal FM material would provide a fully spin polarized current [1] and should possess "engineering compatibility" with its SC host, which includes controllable epitaxy and interfaces, and suitability for device processing. Certain half-metallic ferromagnetic (HMF) materials have a density-of-states (DOS) spin polarisation at the Fermi level of P DOS = 100% due to the presence of a band gap straddling the Fermi energy E F for one spin channel only [2]. Density functional theory (DFT) has predicted this property in several classes of materials [1], including Heusler alloys and transition metal pnictides (TMPs), at temperature T = 0K. On this basis, half-metallicity was first envisaged in NiMnSb, which has a minority spin gap E g ≈ 0.5 eV [3]. However, there is presently no HMF candidate with SC engineering compatibility which clearly maintains P DOS ≈ 100% at room temperature.Experimental verification of P DOS is not straightforward and after more than two decades' study, P DOS (T ) for NiMnSb is not known. Positron annihilation experiments on bulk NiMnSb at T = 27K support P DOS ≈ 100% [4]. Spin polarized photoemission spectroscopy (SPPES) can, in principle, measure P DOS more directly but it is strongly affected by the magnetic, chemical and structural conditions of the surface, which may differ from those of the bulk. Threshold SPPES measured [20]. It is crucial to address the intrinsic limitations on P DOS . It has been realised that HMF band structures change as T increases, even well below the Curie temperature T C [21][22][23][24]. The DOS in the minority spin gap becomes nonzero as the thermal fluctuations produce disorder in the local spin moment alignment. In fact, beyond a threshold temperature T * < T C , the value of P DOS collapses far more rapidly than the reduction of magnetisation M (T ) [22].We report here the successful stabilization of bulklike c-MnSb and w-MnSb crystallites within fully relaxed n-MnSb films grown by molecular beam epitaxy (MBE) on GaAs(111). We confirm by DFT that these are HMF materials at T = 0K. However, we also calculate P DOS as a function of magnetization M (T ) using nonzero-temperature DFT, and...

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“…The [100] direction of NiMnSb and [110] direction of MgO show a nearly perfect lattice match, whereas the lattice mismatch between NiMnSi (100) and MgO (100) is about 10%. This explains why the NiMnSb/MgO interface could be realized experimentally − but the NiMnSi/MgO (100) system could not.…”

Section: Structure and Computational Methodsmentioning

confidence: 99%

Fate of Half-Metallicity Near Interfaces: The Case of NiMnSb/MgO and NiMnSi/MgO

Zhang

Eckern

Schwingenschlögl

2014

ACS Appl. Mater. Interfaces

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The electronic and magnetic properties of the interfaces between the half-metallic Heusler alloys NiMnSb, NiMnSi and MgO have been investigated using first-principles density-functional calculations with projector augmented wave potentials generated in the generalized gradient approximation. In the case of the NiMnSb/MgO (100) interface the half-metallicity is lost, whereas the MnSb/MgO contact in the NiMnSb/MgO (100) interface maintains a substantial degree of spin polarization at the Fermi level (∼ 60%). Remarkably, the NiMnSi/MgO (111) interface shows 100% spin polarization at the Fermi level, despite considerable distortions at the interface, as well as rather short Si/O bonds after full structural optimization. This behavior markedly distinguishes NiMnSi/MgO (111) from the corresponding NiMnSb/CdS and NiMnSb/InP interfaces. PACS numbers: 71.15.Mb, 75.70.Cn,

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Spin polarization at the NiMnSb/MgO(100) interface

Cited by 21 publications

References 28 publications

Direct evidence for minority spin gap in theCo2MnSiHeusler compound

Direct evidence for minority spin gap in theCo2MnSiHeusler compound

Cubic MnSb: Epitaxial growth of a predicted room temperature half-metal

Fate of Half-Metallicity Near Interfaces: The Case of NiMnSb/MgO and NiMnSi/MgO

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