Electronic quasiparticle structure of a thin ferromagnetic local-moment film

Schiller, R.; Müller, W.; Nolting, Wolfgang

doi:10.1016/s0304-8853(96)00711-1

Cited by 13 publications

(31 citation statements)

References 25 publications

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“…This is one important reason why anisotropies play a fundamental role for the understanding of thermodynamic phase transitions in thin films. This restriction however, does not suppress the main physical aspects at T =0 K. The spin splitting in density of states of tunneling electrons is the main origin of the electron-spin polarization, and is independent of the FMS layers thickness [13]. Thus we do not inspect how the spin system is affected by the reduced translational symmetry.…”

Section: Model and Formalismmentioning

confidence: 99%

Spin-polarized tunneling in ferromagnetic double barrier junctions

Saffarzadeh

2001

Eur. Phys. J. B

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Spin-polarized tunneling in FMS/M/FMS double tunnel junctions where FMSs are ferromagnetic semiconductor layers and M is a metal spacer is studied theoretically within the single-site coherent potential approximation (CPA). The exchange interaction between a conduction electron and localized moment of the magnetic ion is treated in the framework of the s-f model. The spin polarization in the FMS layers is observed to oscillates as a function of the number of atomic planes in the spacer layer. Amplitude of these oscillations decreases with increasing the exchange interaction in FMS layers. PACS

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Section: Model and Formalismmentioning

confidence: 99%

Spin-polarized tunneling in ferromagnetic double barrier junctions

Saffarzadeh

2001

Eur. Phys. J. B

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“…For the limiting case of ferromagnetic saturation of the localized f-spin system (T = 0), there exists an exact solution for the FKLM with empty conduction band (n = 0) [12]. While the spin-↓ spectrum exhibits strong correlation effects, the spectrum of the spin-↑ electron is only rigidly shifted compared to the free solution obtained for the case of vanishing s-f interaction, J = 0.…”

mentioning

confidence: 92%

Prediction of a Surface State and a Related Surface Insulator-Metal Transition for the (100) Surface of Stochiometric EuO

Schiller

Nolting

2001

Phys. Rev. Lett.

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We calculate the temperature and layer-dependent electronic structure of a 20-layer EuO(100)-film using a combination of first-principles and model calculation based on the ferromagnetic Kondolattice model. The results suggest the existence of a EuO(100) surface state which can lead to a surface insulator-metal transition.In the recent past many theoretical and experimental research works have been focussed on the intriguing properties of rare earth metals and their compounds. Among others, the extraordinary surface magnetic properties of the lanthanides [1], as e. g. an enhanced Curie temperature of the Gd(0001) surface compared to that of bulk Gd [2], have provoked numerous research activities. Concerning the interplay between electronic structure and exceptional magnetic properties at the Gadolinium surface a Gd(0001) surface state [3,4] is believed to play a crucial role and its temperature dependent behaviour has been discussed intensely, e. g, [5].Rare-earth materials are so-called local-moment systems, i.e. the magnetic moment stems from the partially filled 4f-shell of the rare-earth atom being strictly localized at the ion site. Thus the magnetic properties of these materials are determined by the localized magnetic moments. On the other hand, the electronic properties like electrical conductivity are borne by itinerant electrons in rather broad conduction bands, e.g. 6s, 5d for Gd. Many of the characteristics of local-moment systems can be attributed to a correlation between the localized moments and the itinerant conduction electrons. For this situation the ferromagnetic Kondo-lattice model (FKLM) which is also referred to as the s-f model has been proven to be an adequate description. In this model, the correlation between localized moments and conduction electrons is represented by an intraatomic exchange interaction.In this work we will introduce a multi-band FKLM and use it to calculate the temperature and layer-dependent bandstructure of EuO films. For all the calculations, the surfaces of the films are parallel to the fcc(100) crystal plane and the films will be referred to as EuO(100) films. These films consist of n equivalent parallel layers. The lattice sites within the film are indicated by a greek letter α, β, γ, . . . , denoting the layer, and by a latin letter i, j, k, . . . , numbering the sites within a given layer. The different subbands of the conduction bands of EuO will be denoted by the indices m, m ′ .The Hamiltonian for the multi-band FKLM,consists of three parts. The first,contains the kinetic energy of the conduction band electrons. c + iαmσ (c iαmσ ) is the creation (annihilation) operator of an electron with spin σ from the m-th subband at the lattice site R iα . The T mm ′ ijαβ describe the hopping between the m-th subband at the lattice site R iα and the m ′ -th subband at the lattice site R jβ . These hopping integrals have to be determined within a first-principles band-structure calculation.The second part of the Hamiltonian represents the system of the localized f-momen...

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“…Additionally to the dependence on the s-f exchange interaction and the temperature dependence we notice that the spectral density and the density of states show a typical layer dependence due to the broken translational symmetry at the surfaces of the film. 28 For the center layers (␣ϭ10,11) of the 20-layer film we see from Fig. 8 that the local density of states of the spin-↑ electron at T ϭ0 has already become pretty similar to the well-known tight-binding density of states of the three-dimensional s.c. lattice whereas the density of states of the surface layers (␣ϭ1,20) exhibits the characteristic semi-elliptic profile.…”

Section: ͑41͒mentioning

confidence: 60%

“…The low-energetic part of the spectrum is a scattering band which corresponds to the simple emission of a magnon by the spin-↓ electron, which is necessarily connected with a spin-flip of the electron. 28 From the spectral density of Fig. 3 we get, using Eq.…”

Section: ͑41͒mentioning

confidence: 99%

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Temperature-dependent band structure of a ferromagnetic semiconductor film

Schiller

Nolting

1999

Phys. Rev. B

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The electronic quasiparticle spectrum of a ferromagnetic film is investigated within the framework of the sf model. Starting from the exact solvable case of a single electron in an otherwise empty conduction band being exchange coupled to a ferromagnetically saturated localized spin system we extend the theory to finite temperatures. Our approach is a moment-conserving decoupling procedure for suitable defined Green functions. The theory for finite temperatures evolves continuously from the exact limiting case. The restriction to zero conduction band occupation may be regarded as a proper model description for ferromagnetic semiconductors such as EuO and EuS. Evaluating the theory for a simple cubic film cut parallel to the ͑100͒ crystal plane, we find some marked correlation effects which depend on the spin of the test electron, on the exchange coupling, and on the temperature of the local-moment system.

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Electronic quasiparticle structure of a thin ferromagnetic local-moment film

Cited by 13 publications

References 25 publications

Spin-polarized tunneling in ferromagnetic double barrier junctions

Spin-polarized tunneling in ferromagnetic double barrier junctions

Prediction of a Surface State and a Related Surface Insulator-Metal Transition for the (100) Surface of Stochiometric EuO

Temperature-dependent band structure of a ferromagnetic semiconductor film

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