Extensions to the Kondo lattice model to achieve realistic Curie temperatures and appropriate behavior of the resistivity for manganites

Stier, Martin; Nolting, Wolfgang

doi:10.1103/physrevb.75.144409

Cited by 25 publications

(29 citation statements)

References 28 publications

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“…It was recognized that the orbital degeneracy plays a crucial role both in the double exchange [129] and for the interactions with the lattice due to the JT effect [136], and phase diagrams which resemble the qualitative behavior of the doped manganites were obtained [137]. However, a more realistic treatment requires also electron correlations among e g electrons which are more difficult to implement [8].…”

Section: Coexisting Charge and Orbital Ordermentioning

confidence: 99%

Charge and Orbital Order in Transition Metal Oxides

Oleś

2010

Acta Phys. Pol. A

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A short introduction to the complex phenomena encountered in transition metal oxides with either charge or orbital or joint charge-and-orbital order, usually accompanied by magnetic order, is presented. It is argued that all the types of above ordered phases in these oxides follow from strong Coulomb interactions as a result of certain compromise between competing instabilities towards various types of magnetic order and optimize the gain of kinetic energy in doped systems. This competition provides a natural explanation of the stripe order observed in doped cuprates, nickelates and manganites. In the undoped correlated insulators with orbital degrees of freedom the orbital order stabilizes particular types of anisotropic magnetic phases, and we contrast the case of decoupled (disentangled) spin and orbital degrees of freedom in the manganites with entangled spin-orbital states which decide about certain rather exotic phenomena observed in the perovskite vanadates at finite temperature. Examples of successful concepts in the theoretical approaches to these complex systems are given and some open problems of current interest are indicated. Degrees of freedom in transition metal oxidesThe physical properties of transition metal oxides are driven by strong electron interactions [1]. It is due to strong local Coulomb interactions that these systems exhibit very interesting and quite diverse instabilities towards ordered magnetic phases when doping x or temperature T is varied -is some cases also with orbital order. These instabilities are observed, inter alia, in rapid changes of the transport properties at the metalinsulator phase transitions, or in the onset of superconductivity.One of the outstanding problems in modern condensed matter theory is the description of strongly correlated electrons in various systems. When local Coulomb interactions are strong, the usual methods used for calculating the electronic structure fail and have to be extended by the terms following from local interactions, either in the framework of the local density approximation (LDA) with Coulomb U , the so-called LDA+U method [2], or by the self-energy within the dynamical mean-field theory (DMFT) [3], in the LDA + DMFT approach [4]. This latter approach makes use of the local self-energy which becomes exact in the limit of infinite spatial dimension d = ∞ [5]. However, even these methods cannot overcome certain shortcomings of the effective one-particle theory which justifies modelling of the transition metal * Dedicated to the memory of the late Professor Jan Stankowski. * * e-mail: a.m.oles@fkf.mpg.de oxides with Hamiltonians of the Hubbard type, and looking for solutions with methods of quantum many-body theory. The advantage of recent rapid progress in the electronic structure calculations is that such models can use realistic parameters nowadays, which follow from the electronic structure calculations for a given system. Although the field of strongly correlated electronic systems is very rich, we shall concentrate here on the phe...

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Section: Coexisting Charge and Orbital Ordermentioning

confidence: 99%

Charge and Orbital Order in Transition Metal Oxides

Oleś

2010

Acta Phys. Pol. A

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“…Fig. 9) whereas the saturation effect is more visible for the case of T to start at larger couplings 17,38 . Again the difference between the Curie temperatures of both configurations is interesting for coupled film systems.…”

Section: B Curie Temperaturesmentioning

confidence: 88%

“…With the calculation of the Green's function we also get the important quantity of the internal energy (38) which can be used to compare the energies of different phases.…”

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confidence: 99%

Carrier-mediated interlayer exchange, ground-state phase diagrams, and transition temperatures of magnetic thin films

Stier

Nolting

2011

Phys. Rev. B

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We investigate the influence of the carrier density and other parameters on the interlayer exchange in magnetic thin film systems. The system consists of ferromagnetic and non-magnetic layers where the carriers are allowed to move from layer to layer. For the ferromagnetic layers we use the Kondolattice model to describe interactions between itinerant electrons and local moments. The electrons' properties are calculated by a Green's function's equation of motion approach while the magnetization of the local moments is determined by a minimization of the free energy. As results we present magnetic phase diagrams and the interlayer exchange over a broad parameter range. Additionally we can calculate the transition temperatures for different alignments of the ferromagnetic layers' magnetizations.

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“…The earlier theoretical ideas were based on the double exchange model, 22 which can be understood as one of the limiting cases of Kondo lattice model ͑i.e., limit of strong Hunds coupling͒. Although recent theories 23 have provided a step forward, its complete understanding is far from being explained by any current physical theories. As compared to the aforementioned compounds, the heavy fermion systems 24 ͑mostly Ce compounds͒ are known to have antiparallel alignment of the conduction electron and localized spins.…”

Section: Introductionmentioning

confidence: 95%

Ferromagnetism in the multiband Kondo lattice model

Sharma

Nolting

2008

Phys. Rev. B

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The ferromagnetic spin-exchange interaction between the itinerant electrons and localized moments on a periodic lattice, studied within the so-called Kondo lattice model, is considered for multiband situation where the hopping integral is a matrix in general. The modified Ruderman-Kittel-Kasuya-Yosida theory, wherein one can map such a model onto an effective Heisenberg-type system, is extended to a multiband case with finite bandwidth and hybridization on a simple-cubic lattice. As an input for the evaluation of the effective exchange integrals, one requires the multiband electronic self-energy, which is taken from an earlier proposed ansatz. Using the above procedure, we determine the magnetic properties of the system such as Curie temperature while calculating the chemical potential and magnetization within a self-consistent scheme for various values of system parameters. The results are discussed in detail and the model is motivated in order to study the electronic, transport, and magnetic properties of real materials like GdN.

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Extensions to the Kondo lattice model to achieve realistic Curie temperatures and appropriate behavior of the resistivity for manganites

Cited by 25 publications

References 28 publications

Charge and Orbital Order in Transition Metal Oxides

Charge and Orbital Order in Transition Metal Oxides

Carrier-mediated interlayer exchange, ground-state phase diagrams, and transition temperatures of magnetic thin films

Ferromagnetism in the multiband Kondo lattice model

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