Surface spin polarization of the nonstoichiometric Heusler alloy Co<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>MnSi

Wüstenberg, Jan-Peter; Fetzer, Roman; Aeschlimann, Martin; Cinchetti, Mirko; Minář, J.; Braun, Jürgen; Ebert, H.; Ishikawa, Takayuki; Uemura, Tetsuya; Yamamoto, Mikio

doi:10.1103/physrevb.85.064407

Cited by 49 publications

(32 citation statements)

References 46 publications

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“…Picozzi et al predicted from first principles that half-metallicity in CMS and Co 2 MnGe (CMG) is lost for Co Mn antisites, where a Mn site is replaced by a Co atom, because of the appearance of minority-spin in gap states near E F , while half-metallicity is retained for Mn Co antisites, where a Co site is replaced by a Mn atom [33]. The effect of off-stoichiometry on the half-metallicity of CMS and CMG has been systematically investigated recently using various experimental approaches, including the tunneling magnetoresistance (TMR) ratios of MTJs [9][10][11][12], the saturation magnetization per formula unit of thin films [12], the surface spin polarization [42], the magnetic states as investigated by x-ray absorption spectroscopy and x-ray magnetic circular dichroism [43][44][45], and the electronic states as investigated through spin-resolved low-energy and hard x-ray photoelectron spectroscopy [46][47][48]. These experimental studies, along with first-principles calculations, demonstrated that Co Mn antisites induced by a Mn-deficient composition (the Mn composition α < 2 − β in the composition expression of Co 2 Mn α Si β ) is detrimental to the half-metallicity of CMS.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of spin-dependent tunneling conductance of magnetic tunnel junctions with half-metallicCo2MnSielectrodes

Moges

Honda

et al. 2016

Phys. Rev. B

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In order to elucidate the origin of the temperature (T ) dependence of spin-dependent tunneling conductance (G) of magnetic tunnel junctions (MTJs), we experimentally investigated the T dependence of G for the parallel and antiparallel magnetization alignments, G P and G AP , of high-quality Co 2 MnSi (CMS)/MgO/CMS MTJs having systematically varied spin polarizations (P ) at 4.2 K by varying the Mn composition α in Co 2 Mn α Si electrodes that exhibited giant tunneling magnetoresistance ratios. Results showed that G P normalized by its value at 4.2 K exhibited a notable, nonmonotonic T dependence although its variation with T was significantly smaller than that of G AP normalized by its value at 4.2 K, indicating that an analysis of the experimental G P (T ) is critical to revealing the origin of the T dependence of G. By analyzing the experimental G P (T ), we clarified that both spin-flip inelastic tunneling via a thermally excited magnon and spin-conserving elastic tunneling in which P decays with increasing T play key roles. The experimental G AP (T ), including its stronger T dependence for higher P at 4.2 K, was also consistently explained with this model. Our findings provide a unified picture for understanding the origin of the T dependence of G of MTJs with a wide range of P , including MTJs with high P close to a half-metallic value.

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Section: Introductionmentioning

confidence: 99%

Temperature dependence of spin-dependent tunneling conductance of magnetic tunnel junctions with half-metallicCo2MnSielectrodes

Moges

Honda

et al. 2016

Phys. Rev. B

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“…In previous studies, we demonstrated high tunneling magnetoresistance (TMR) ratios of up to 1995% at 4.2 K and up to 354% at 290 K in magnetic tunnel junctions (MTJs) having Mn-rich Co 2 MnSi (CMS) electrodes [27], and 2610% at 4.2 K and 429% at 290 K in Co 2 (Mn,Fe)Si (CMFS) MTJs [28]. We have experimentally shown that harmful defects in CMS, CMFS, and Co 2 MnGe thin films-i.e., Co Mn antisites -can be suppressed by a Mn-rich composition [27][28][29][30][31][32]. Furthermore, we have achieved efficient spin injection from Mn-rich CMS into GaAs via an ultrathin Co 50 Fe 50 (CoFe) insertion layer, resulting in electron spin polarization (P GaAs ) of up to 52% at ferromagnet/GaAs interface at 4.2 K [33].…”

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confidence: 94%

Coherent manipulation of nuclear spins using spin injection from a half-metallic spin source

et al. 2016

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We have developed a nuclear magnetic resonance (NMR) system that uses spin injection from a highly polarized spin source. Efficient spin injection into GaAs from a half-metallic spin source of Mn-rich Co 2 MnSi enabled an efficient dynamic nuclear polarization of Ga and As nuclei in GaAs and a sensitive detection of NMR signals. Moreover, coherent control of nuclear spins, or the Rabi oscillation between two quantum levels formed at Ga nuclei, induced by a pulsed NMR has been demonstrated at a relatively low magnetic field of ∼0.1 T. This provides a novel all-electrical solid-state NMR system with the high spatial resolution and high sensitivity needed to implement scalable nuclear-spin-based qubits. Nuclear spins in semiconductors are an ideal system for implementing quantum bits (qubits) for quantum computation because they have an extremely long coherence time. The nuclear magnetic resonance (NMR) technique enables the control and detection of nuclear-spin qubits, and quantum algorism with seven qubits has been demonstrated in molecules in a liquid [1]. For large-scale integration, however, the implementation of qubits in solid-state materials, especially in semiconductors, is indispensable. Moreover, in conventional NMR techniques, a strong magnetostatic field should be applied to polarize nuclear spins, making it difficult to selectively control nuclear spins located within nanometer-sized regions. Furthermore, since the magnetic moment of a nuclear spin is three orders of magnitude smaller than that of an electron spin, the sensitivity of detecting nuclear spins through a pickup coil is quite low. Thus, there is a strong need to develop a novel NMR technique with high spatial resolution and high sensitivity to enable a future large-scale quantum computing system. From this point of view, dynamic nuclear polarization (DNP), where nuclear spins are dynamically polarized through a hyperfine interaction between nuclear spins and electron spins, has attracted much interest, since it can drastically increase the NMR signal. Several solid-state NMR devices based on different DNP techniques by optical [2][3][4] or electrical means [5][6][7] have recently been reported. Furthermore, coherent manipulation of nuclear spins, or the Rabi oscillation, which is a key factor for nuclear-spin-based qubits, has been demonstrated electrically in GaAs/AlGaAs quantum Hall systems [8][9][10] and optically in GaAs/AlGaAs quantum wells [11,12]. Although the optical method is suitable for clarifying the fundamental physics relevant to nuclear spins, it is restricted in its scalability because the spatial resolution is limited by the optical wavelength. Quantum Hall systems, on the other hand, require a relatively strong magnetic field of several tesla and a low temperature below 1 K to create the highly spin-polarized electrons necessary for the DNP and the detection of nuclear-spin states.An injection of spin-polarized electrons from a ferromagnetic electrode into a semiconductor also creates spinpolarized electronic states in a ...

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“…Therefore in combination with the LSDA+DMFT, the simultaneous description of the orbital magnetic moments [8][9][10], relativistic band structure [11], hyperfine fields [12], spin-fluctuations [13], and accurate total energy calculations [14] becomes possible. In the later years, this method was successfully applied to a variety of disordered magnetic systems including transition metal [9,15], Heusler alloys [16,17] and diluted magnetic semi-conductors systems [18,19]. Furthermore, correlation effects on the hcp-Co(0001) surface have been studied and showed pronounced changes in the band structure seen when the magnetisation is oriented in or out-of-plane, as a consequence of the spin-orbit coupling acting on the electronic states [20].…”

Section: Introductionmentioning

confidence: 99%

A self-consistent, relativistic implementation of the LSDA+DMFT method

Minář

Ebert²,

Chioncel

2017

Eur. Phys. J. Spec. Top.

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Abstract. In this review we report on developments and various applications of the combined Density Functional and Dynamical Mean-Field Theory, the so-called LSDA + DMFT method, as implemented within the fully relativistic KKR (Korringa-Kohn-Rostoker) band structure method. The KKR uses a description of the electronic structure in terms of the single-particle Green function, which allows to study correlation effects in ordered and disordered systems independently of its dimensionality (bulk, surfaces and nano-structures). We present self-consistent LSDA+DMFT results for the ground state and spectroscopic properties of transition metal elements and their compounds. In particular we discuss the spin-orbit induced orbital magnetic moments for Fe xNi1−x disordered alloys, the magnetic Compton profiles of fcc Ni and the angle-resolved photoemission spectroscopy (ARPES) spectra for gallium manganese arsenide dilute magnetic semiconductors. For the (GaMn)As system a direct comparison with the experimental ARPES spectra demonstrates the importance of matrix element effects, the presence of the semi-infinite surface and the inclusion of layer-dependent self-energies.

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Surface spin polarization of the nonstoichiometric Heusler alloy Co2MnSi

Cited by 49 publications

References 46 publications

Temperature dependence of spin-dependent tunneling conductance of magnetic tunnel junctions with half-metallicCo2MnSielectrodes

Temperature dependence of spin-dependent tunneling conductance of magnetic tunnel junctions with half-metallicCo2MnSielectrodes

Coherent manipulation of nuclear spins using spin injection from a half-metallic spin source

A self-consistent, relativistic implementation of the LSDA+DMFT method

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