Theory of ferromagnetic semiconductors

Nolting, Wolfgang

doi:10.1002/pssb.2220960102

Cited by 164 publications

(90 citation statements)

References 80 publications

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“…Usually, one would expect that emission of magnons in the spin chain will lead to a relaxation and dephasing of the electron spins antiparallel to the spin direction of the spin chain, leading to incoherent transport for this spin direction. However, it was shown in several works on ferromagnetic semiconductors [11,12,13,14] that a single electron with antiparallel spin direction to the localized spins can hybridize with one-magnon states to form the so-called magnetic polaron states. These states form a band which is separated from the band of scattering states, and therefore have a low decoherence rate.…”

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confidence: 99%

Fingerprints of the Magnetic Polaron in Nonequilibrium Electron Transport through a Quantum Wire Coupled to a Ferromagnetic Spin Chain

2006

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We study nonequilibrium quantum transport through a mesoscopic wire coupled via local exchange to a ferromagnetic spin chain. Using the Keldysh formalism in the self-consistent Born approximation, we identify fingerprints of the magnetic polaron state formed by hybridization of electronic and magnon states. Because of its low decoherence rate, we find coherent transport signals. Both elastic and inelastic peaks of the differential conductance are discussed as a function of external magnetic fields, the polarization of the leads and the electronic level spacing of the wire.

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confidence: 99%

Fingerprints of the Magnetic Polaron in Nonequilibrium Electron Transport through a Quantum Wire Coupled to a Ferromagnetic Spin Chain

2006

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“…This direction is called zdirection hereafter and the system occupies the half-space z > 0. We use the s-f model which is commonly considered as realistic for local-moment structures 19,21,22 . In this model the following Hamiltonian is used to describe the magnetic semi-infinite crystal:…”

Section: Model and Formalismmentioning

confidence: 99%

Temperature dependence of surface magnetization in local-moment systems

Saffarzadeh

2006

Surface Science

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We present a theory to study the temperature-dependent behavior of surface states in a ferromagnetic semi-infinite crystal. Our approach is based on the single-site approximation for the s-f model. The effect of the semi-infinite nature of the crystal is taken into account by a localized perturbation method. Using the mean-field theory for the layer-dependent magnetization, the local density of states and the electron-spin polarization are investigated at different temperatures for ordinary and surface transition cases. The results show that the surface magnetic properties may differ strongly from those in the bulk and the coupling constant of atoms plays a decisive role in the degree of spin polarization. In particular, for the case in which the exchange coupling constant on the surface and between atoms in the first and second layer is higher than the corresponding in the bulk, an enhancement of surface Curie temperature and hence the spin polarization can be obtained.

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“…The Kondo-lattice model (or s-f model) traces back the characteristic features of the underlying physical system to an interband exchange coupling of itinerant conduction electrons to (quasi-) localized magnetic moments described by the following model Hamiltonian [5,6] …”

Section: Hamiltonianmentioning

confidence: 99%

Quantum effects in the quasiparticle structure of the ferromagnetic Kondo lattice model

Meyer¹,

Santos

Nolting

2001

J. Phys.: Condens. Matter

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Abstract.A new "Dynamical Mean-field theory" based approach for the Kondo lattice model with quantum spins is introduced. The inspection of exactly solvable limiting cases and several known approximation methods, namely the second-order perturbation theory, the self-consistent CPA and finally a momentconserving decoupling of the equations of motion help in evaluating the new approach. This comprehensive investigation gives some certainty to our results: Whereas our method is somewhat limited in the investigation of the J < 0-model, the results for J > 0 reveal important aspects of the physics of the model: The energetically lowest states are not completely spin-polarized. A band splitting, which occurs already for relatively low interaction strengths, can be related to distinct elementary excitations, namely magnon emission (absorption) and the formation of magnetic polarons. We demonstrate the properties of the ferromagnetic Kondo lattice model in terms of spectral densities and quasiparticle densities of states.

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Theory of ferromagnetic semiconductors

Cited by 164 publications

References 80 publications

Fingerprints of the Magnetic Polaron in Nonequilibrium Electron Transport through a Quantum Wire Coupled to a Ferromagnetic Spin Chain

Fingerprints of the Magnetic Polaron in Nonequilibrium Electron Transport through a Quantum Wire Coupled to a Ferromagnetic Spin Chain

Temperature dependence of surface magnetization in local-moment systems

Quantum effects in the quasiparticle structure of the ferromagnetic Kondo lattice model

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