Related papers: Ferromagnetism in Electronic Models for Manganites
We construct the 1/S spin-wave expansion for double exchange ferromagnets at T=0. It is assumed that the value of Hund's rule coupling, J_H, is sufficiently large, resulting in a fully saturated, ferromagnetic half-metallic ground state. We…
Semiconductor nano-devices have been scaled to the level that transport can be dominated by a single dopant atom. In the strong coupling case a Kondo effect is observed when one electron is bound to the atom. Here, we report on the spin as…
We introduce a new approach to the periodic Anderson model (PAM) that allows a detailed investigation of the magnetic properties in the Kondo as well as the intermediate valence regime. Our method is based on an exact mapping of the PAM…
The magnetic properties of the ferromagnetic Kondo-lattice model (FKLM) are investigated. Starting from an analysis of the magnon spectrum in the spin-wave regime, we examine the ferromagnetic stability as a function of the occupation of…
We analyze the transitions that a magnetic field provokes in the ground state of an artificial homonuclear diatomic molecule. For that purpose, we have performed numerical diagonalizations for a double quantum dot around the regime of…
We consider the one-orbital $N$-site repulsive Hubbard model on two kagome-like chains, both of which yield a completely dispersionless (flat) one-electron band. Using exact many-electron ground states in the subspaces with $n\le n_{\max}$…
A ferromagnetic insulating (FM-I) state in Pr0.75Ca0.25MnO3 has been studied by neutron scattering experiment and theoretical calculation. The insulating behavior is robust against an external magnetic field, and is ascribed to neither the…
Polycrystalline samples of the quarter-doped manganites $R_{0.75}$Ca$_{0.25}$MnO$_3$ ($R$ = Y, Tb, Dy, Ho, and Er) were studied by X-ray diffraction and AC/DC susceptibility measurements. All five samples are orthorhombic and exhibit…
The influence of local electronic correlations on the properties of colossal magnetoresistance manganites is investigated. To this end, a ferromagnetic two-band Kondo lattice model is supplemented with the local Coulomb repulsion missing in…
The paramagnetic insulator to ferromagnetic metal transition in Lanthanum manganites and the associated magnetoresistive phenomena is treated by considering the localization due to random hopping induced by slowly fluctuating spin…
The electron-electron correlations in a many-electron (Ne = 1, 2,..., 5) quantum dot confined by a parabolic potential is investigated in the presence of a single magnetic ion and a perpendicular magnetic field. We obtained the energy…
Performing an exact diagonalization of the effective spin problem, a ferromagnetic ground state of kinetic origin is shown to emerge in a system of $N$ strongly correlated electrons on a $L$-site ring ($L > N$). This phenomenon is brought…
The one-dimensional Kondo lattice model is investigated by using bosonization techniques and conformal field theory. In the half-filled band, the charge and spin gaps open for the anti-ferromagnetic Kondo coupling. Away from half-filling,…
Double-exchange model in infinite dimension is studied as the strong Hund's coupling limit $J\to\infty$ of the Kondo lattice model. Several quantities such as Green's function and the d.c.\ conductivity are calculated in analytical forms.…
We study numerically the one-dimensional ferromagnetic Kondo lattice. This model is widely used to describe nickel and manganese perovskites. Due to the competition between double and super-exchange, we find a region where the formation of…
We present the T=0 phase diagram of the double-exchange model (ferromagnetic Kondo lattice model) for all values of the carrier concentration $n$ and Hund's couplng $J$, within dynamical mean field theory. We find that depending on the…
Magnon self energy due to spin-charge coupling is calculated for the correlated ferromagnetic Kondo lattice model using a diagrammatic expansion scheme. Systematically incorporating correlation effects in the form of self-energy and vertex…
Magnetic field effects in Kondo insulators are studied theoretically, using a local moment approach to the periodic Anderson model within the framework of dynamical mean-field theory. Our main focus is on field-induced changes in…
We propose a variational wave function for the ground state of the magnetic heavy fermion (HF) systems, in which both the Kondo and the RKKY interactions are variationally incorporated and the local f-orbital state exists as a linear…
Using inelastic neutron scattering we measured the microscopic magnetic coupling associated with the ferromagnetic (FM) clusters of the ``colossal magnetoresistance'' (CMR) compound Pr$_{0.70}$Ca$_{0.30}$MnO$_3$. When the insulating to…