Determining Exchange Splitting in a Magnetic Semiconductor by Spin-Filter Tunneling

Santos, Tiffany S.; Moodera, Jagadeesh S.; Raman, Karthik V.; Negusse, Ezana; Holroyd, J.; Dvorak, Joseph; Liberati, M.; Idzerda, Y. U.; Arenholz, Elke

doi:10.1103/physrevlett.101.147201

Cited by 131 publications

(120 citation statements)

References 24 publications

(22 reference statements)

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“…As electrode material, we consider fcc Cu oriented along the [001] direction (lattice constant 3.61Å), which is a material choice that has been adopted in several experiments. [17][18][19][20] When the tetragonal EuO unit cell is used, the lattice constant of Cu can be matched with only a slight strain to the EuO lattice, since the dimensions along x and y are a EuO / √ 2 = 3.63Å. The junction setup is illustrated in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…3 SFTJs based on polycrystalline EuO in the form of a metal/EuO/metal heterojunction have been studied in several recent experiments. [16][17][18][19][20][21][22] However, the spin transport properties of crystalline epitaxial EuO junctions have not been studied theoretically so far. The purpose of this paper is to provide such theoretical insight.…”

Section: T (E) ∝ Exp[−2κ( E)t] With κ( E) = √mentioning

confidence: 99%

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Electronic transport through EuO spin-filter tunnel junctions

et al. 2012

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Epitaxial spin-filter tunnel junctions based on the ferromagnetic semiconductor europium monoxide (EuO) are investigated by means of density functional theory. In particular, we focus on the spin transport properties of Cu(100)/EuO(100)/Cu(100) junctions. The dependence of the transmission coefficient and the current-voltage curves on the interface spacing and EuO thickness is explained in terms of the EuO density of states and the complex band structure. Furthermore, we also discuss the relation between the spin transport properties and the Cu-EuO interface geometry. The level alignment of the junction is sensitively affected by the interface spacing, since this determines the charge transfer between EuO and the Cu electrodes. Our calculations indicate that EuO epitaxially grown on Cu can act as a perfect spin filter, with a spin polarization of the current close to 100%, and with both the Eu-5d conduction-band and the Eu-4f valence-band states contributing to the coherent transport. For epitaxial EuO on Cu, a symmetry filtering is observed, with the 1 states dominating the transmission. This leads to a transport gap larger than the fundamental EuO band gap. Importantly, the high spin polarization of the current is preserved up to large bias voltages.

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Section: Methodsmentioning

confidence: 99%

Section: T (E) ∝ Exp[−2κ( E)t] With κ( E) = √mentioning

confidence: 99%

Electronic transport through EuO spin-filter tunnel junctions

et al. 2012

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“…They have been used for decades to generate polarized currents in spintronic circuits. 23,24 In spite of numerous works devoted to the theoretical study of S/F structures, the study of the spin-filter effect in connection with the transport properties of S/F structures still remains open. For example, in Ref.…”

Section: Introductionmentioning

confidence: 99%

Electronic transport through ferromagnetic and superconducting junctions with spin-filter tunneling barriers

2012

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We present a theoretical study of the quasiparticle and subgap conductance of generic X/I sf /S M junctions with a spin-filter barrier I sf , where X is either a normal N or a ferromagnetic metal F and S M is a superconductor with a built-in exchange field. Our study is based on the tunneling Hamiltonian and the Green's-function technique. First, we focus on the quasiparticle transport, both above and below the superconducting critical temperature. We obtain a general expression for the tunneling conductance which is valid for arbitrary values of the exchange field and arbitrary magnetization directions in the electrodes and in the spin-filter barrier. In the second part, we consider the subgap conductance of a N/I sf /S junction, where S is a conventional superconductor. In order to account for the spin-filter effect at interfaces, we heuristically derive boundary conditions for the quasiclassical Green's functions. With the help of these boundary conditions, we show that the proximity effect and the subgap conductance are suppressed by spin filtering in a N/I sf /S junction. Our work provides useful tools for the study of spin-polarized transport in hybrid structures both in the normal and in the superconducting state.

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“…For many years they have attracted interest. For example, EuO has been suggested for applications in spin-filter devices, 5,[31][32][33][34] and EuS ͑Refs. 35-41͒ as well as EuSe ͑Ref.…”

Section: Properties Of Europium Chalcogenidesmentioning

confidence: 99%

Optical third-harmonic spectroscopy of the magnetic semiconductor EuTe

et al. 2010

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EuTe possesses the centrosymmetric crystal structure m3m of rocksalt type in which the second-harmonic generation is forbidden in electric dipole approximation but the third-harmonic generation ͑THG͒ is allowed. We studied the THG spectra of this material and observed several resonances in the vicinity of the band gap at 2.2-2.5 eV and at higher energies up to 4 eV, which are related to four-photon THG processes. The observed resonances are assigned to specific combinations of electronic transitions between the ground 4f 7 state at the top of the valence band and excited 4f 6 5d 1 states of Eu 2+ ions, which form the lowest energy conduction band. Temperature, magnetic field, and rotational anisotropy studies allowed us to distinguish crystallographic and magnetic-field-induced contributions to the THG. A strong modification of THG intensity for the 2.4 eV band and suppression of the THG for the 3.15 eV band was observed in applied magnetic field. Two main features of the THG spectra were assigned to 5d͑t 2g ͒ and 5d͑e g ͒ subbands at 2.4 eV and 3.15 eV, respectively. A microscopic quantum-mechanical model of the THG response was developed and its conclusions are in qualitative agreement with the experimental results.

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Determining Exchange Splitting in a Magnetic Semiconductor by Spin-Filter Tunneling

Cited by 131 publications

References 24 publications

Electronic transport through EuO spin-filter tunnel junctions

Electronic transport through EuO spin-filter tunnel junctions

Electronic transport through ferromagnetic and superconducting junctions with spin-filter tunneling barriers

Optical third-harmonic spectroscopy of the magnetic semiconductor EuTe

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