相关论文: Phase separation in double exchange systems
This article gives a comprehensive review on the recent studies of the double exchange systems using non-perturbative approaches; the dynamical mean-field theory and the Monte Carlo method. Investigations beyond mean-field type treatments…
The phase diagram of the double exchange model is studied in the large-S limit at zero temperature in two and three dimensions. We find that the spiral state has lower energy than the canted antiferromagnetic state in the region between the…
The generic changes of the electronic compressibility in systems which show magnetic instabilities is studied. It is shown that, when going into the ordered phase, the compressibility is reduced by an amount comparable to the its original…
The coexistence of ferromagnetism and metallic conduction in doped manganites has long been explained by a double-exchange model in which the ferromagnetic exchange arises from the carrier hopping. We evaluate the zero-temperature spin…
In the framework of a two-band model, we study the phase separation regime of different kinds of strongly correlated charge carriers as a function of the energy splitting between the two sets of bands. The narrow (wide) band simulates the…
Phase diagram and critical properties are studied for three-dimensional double exchange model with and without quenched disorder. Employing the Monte Carlo method and the systematic analysis on the finite-size effect, we estimate the Curie…
The resistivity around the ferromagnetic transition temperature in the double exchange model is studied by the Schwinger boson approach. The spatial spin correlation responsible for scattering of conduction electrons are taken into account…
A microscopic theory for rare-earth ferromagnetic hexaborides, such as Eu(1-x)Ca(x)B6, is proposed on the basis of the double-exchange Hamiltonian. In these systems, the reduced carrier concentrations place the Fermi level near the mobility…
Effective models are derived from the ferromagnetic Kondo lattice model with classical corespins, which greatly reduce the numerical effort. Results for these models are presented. They indicate that double exchange gives the correct order…
A two-band Hubbard model is used to describe the band structure and phase separation (PS) in multiband superconductors, especially in cuprates. We predict a large peak in the density of states at the Fermi level in the case of optimum…
Doping change and distortion effect on the double-exchange ferromagnetism are studied within a simplified double-exchange model. The presence of distortion is modelled by introducing the Falicov-Kimball interaction between itinerant…
Spin-state transitions, observed in many transition metal compounds containing Co$^{3+}$ and Fe$^{2+}$, may occur with the change of temperature, pressure, but also with doping, in which case the competition of single-site effects and…
We study ferromagnetic transition in three-dimensional double-exchange model. The influence of strong spin fluctuations on conduction electrons is described in coherent potential approximation. In the framework of thermodynamic approach we…
A general quantitative measure of the tendency towards phase separation is introduced for systems exhibiting phase transitions or crossovers controlled by charge carrier concentration. This measure is devised for the situations when the…
Ferromagnetism in Cr-based double perovskites is analyzed using effective model as well as simulation approach. Starting from a microscopic model proposed recently for this class of double perovskites, an effective spin-only model is…
The two-band Hubbard model is used to analyze a possibility of a non-uniform charge distribution in a strongly correlated electron system with two types of charge carriers. It is demonstrated that in the limit of strong on-site Coulomb…
We consider spin-fermion systems which get their magnetic properties from a system of localized magnetic moments being coupled to conducting electrons. The dynamical degrees of freedom are spin-$s$ operators of localized spins and spin-1/2…
It is shown that the double exchange Hamiltonian, with weak antiferromagnetic interactions, has a rich variety of first order transitions between phases with different electronic densities and/or magnetizations. For band fillings in the…
The superconducting properties of a recently proposed phenomenological model for a weakly doped antiferromagnet are analyzed, taking into account fluctuations of the phase of the order parameter. In this model, we assume that the doped…
The attempt to describe the bell-shape dependence of the critical temperature of high-$T_{c}$ superconductors on charge carriers density is made. Its linear increase in the region of small densities (underdoped regime) is proposed to…