Spin-filtering efficiency of ferrimagnetic spinels CoFe<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>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>and NiFe<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>O<mml:math xmlns:mml="http://www.w3.org

Caffrey, Nuala M.; Fritsch, Daniel; Archer, Thomas; Sanvito, Stefano; Ederer, Claude

doi:10.1103/physrevb.87.024419

Cited by 74 publications

(48 citation statements)

References 40 publications

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“…The effective U (i.e. U -J = 3 eV) is applied to Ni-d, Fe-d and Yb-f orbitals and the calculations are carried out using rotationally invariant Dudarev approach [33] The electronic structure of pure NFO has been investigated by many in the past in the context of strong correlation effect [32,34], spin-filter efficiency [3] and stability of normal and inverse spinel configuration [17,30,31]. In the present study, the electronic structure of NFO is revisited in order to examine the effect of substitution of Yb as well as to explain the insulating mechanism of the parent compound.…”

Section: A Computational Detailsmentioning

confidence: 99%

Effect of frustrated exchange interactions and spin-half-impurity on the electronic structure of strongly correlatedNiFe2O4

et al. 2017

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Spin-polarized density functional calculations, magnetization, and neutron diffraction (ND) measurements are carried out to investigate the magnetic exchange interactions and strong correlation effects in Yb substituted inverse spinel nickel ferrite. In the pristine form, the compound is found to be a mixed insulator under the Zaanen-Sawatzky-Allen classification scheme as it features both charge transfer and Mott insulator mechanism. Estimation of magnetic exchange couplings reveals that both octahedral-octahedral and octahedral-tetrahedral spin-spin interactions are antiferromagnetic. This is typical of spin-frustrated triangular lattice with one of the vertices occupied by tetrahedral spins and remaining two are occupied by octahedral spins. However, since the octahedral-tetrahedral interaction is dominant, it leads to a forced parallel alignment of the spins at the octahedral site which is in agreement with the results of ND measurements. The substituent Yb is found to be settled in +3 charge state, as confirmed from the XPS measurements, to behave like a spin-half impurity carried by the localized f z(x 2 −y 2 ) orbital. The impurity f spin significantly weakens the antiferromagnetic coupling with the spins at the tetrahedral site, which explains the experimental observation of fall in Curie temperature with Yb substitution.

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Section: A Computational Detailsmentioning

confidence: 99%

Effect of frustrated exchange interactions and spin-half-impurity on the electronic structure of strongly correlatedNiFe2O4

et al. 2017

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“…29 We set U = 3 eV and J = 0 eV for the d orbitals of both Fe and Co, in accordance with a recent theoretical study. 21 Analysis of the complex band structure is achieved by constructing Wannier orbitals from the GGA + U band structure of bulk CFO (Ref. 30) and using standard tight-binding techniques thereafter.…”

Section: Computational Detailsmentioning

confidence: 99%

“…[19][20][21] In the former, the spin-filter efficiency is entirely determined by the spin-dependent barrier height in the ferromagnetic insulator. The latter approach takes into account the realistic electronic structure of the bulk material, in particular, the orbital character and symmetry of the complex bands.…”

Section: Introductionmentioning

confidence: 99%

Interface states in CoFe2O4spin-filter tunnel junctions

et al. 2013

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Spin-filter tunneling is a promising way to generate highly spin-polarized current, a key component for spintronics applications. In this paper we explore the tunneling conductance across the spin-filter material CoFe 2 O 4 interfaced with Au electrodes, a geometry which provides nearly perfect lattice matching at the CoFe 2 O 4 /Au(001) interface. Using density functional theory calculations we demonstrate that interface states play a decisive role in controlling the transport spin polarization in this tunnel junction. For a realistic CoFe 2 O 4 barrier thickness, we predict a tunneling spin polarization of about −60%. We show that this value is lower than what is expected based solely on considerations of the spin-polarized band structure of CoFe 2 O 4 , and therefore that these interface states can play a detrimental role. We argue that this is a rather general feature of ferrimagnetic ferrites and could make an important impact on spin-filter tunneling applications.

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“…DFT methods are, however, difficult to use for this oxide: The strongly correlated character of the 3d electrons requires the use of complex methods like the DFT + U [25,26,[29][30][31], and the random distribution of Co and Fe atoms in octahedral atomic sites is complicated to take into account.…”

Section: Introductionmentioning

confidence: 99%

Fully spin-polarized two-dimensional electron gas at the <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi mathvariant="normal">CoFe</mi></mrow><mn>2</mn></msub><msub><mrow><mi mathvariant="normal">O</mi></mrow><mn>4</mn></msub><mo>/</mo><msub><mrow><mi mathvariant="normal">MgAl</mi></mrow><mn>2</mn>

Arras

Calmels

2014

Phys. Rev. B

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We performed first-principles calculations to show that a fully spin-polarized two-dimensional electron gas can be created at the interface between the polar and insulating spinel oxides CoFe 2 O 4 and MgAl 2 O 4 . We give a clear description of the physical parameters (in particular the atomic termination of the interfaces), which favor the formation of this electron gas that is due either to an electric field induced in stoichiometric oxide layers because of their polar character or to a charge reorganization that preserves the global electric neutrality in nonstoichiometric layers. We show that the electric field-induced spin-polarized two-dimensional electron gas can only exist if the thickness of the CoFe 2 O 4 layer is large enough and that it may be destroyed by intermixing at the interfaces.

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Spin-filtering efficiency of ferrimagnetic spinels CoFe2O4and NiFe2O
Nuala M. Caffrey
¹
,
Daniel Fritsch
²
,
Thomas Archer
³

et al.

Cited by 74 publications

References 40 publications

Effect of frustrated exchange interactions and spin-half-impurity on the electronic structure of strongly correlatedNiFe2O4

Effect of frustrated exchange interactions and spin-half-impurity on the electronic structure of strongly correlatedNiFe2O4

Interface states in CoFe2O4spin-filter tunnel junctions

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Spin-filtering efficiency of ferrimagnetic spinels CoFe2O4and NiFe2ONuala M. Caffrey1, Daniel Fritsch2, Thomas Archer3 et al.

Cited by 74 publications

References 40 publications

Effect of frustrated exchange interactions and spin-half-impurity on the electronic structure of strongly correlatedNiFe2O4

Effect of frustrated exchange interactions and spin-half-impurity on the electronic structure of strongly correlatedNiFe2O4

Interface states in CoFe2O4spin-filter tunnel junctions

Contact Info

Product

Resources

About

Spin-filtering efficiency of ferrimagnetic spinels CoFe2O4and NiFe2O
Nuala M. Caffrey
¹
,
Daniel Fritsch
²
,
Thomas Archer
³

et al.