Related papers: Spin-lattice coupling effects in the Holstein doub…
Spin excitation spectrum of CMR manganites are studied from both theoretical and experimental sides. Scaling relations for the spin wave lifetime in the electronic model with double-exchange interaction is observed, which is consistent with…
The interplay of spin and lattice fluctuations in two-dimensional magnets without inversion symmetry is investigated. We find a general form for the magnetoelastic coupling between magnons and existing chiral phonons based on the symmetries…
Coupled, dynamical spin-lattice models provide a unique test ground for simulations investigating the finite-temperature magnetic properties of materials under the direct influence of the lattice vibrations. These models are constructed by…
The physics of ferromagnetic doped manganites, such as \chem{La_{1-x}Ca_xMnO_3} with $x\approx0.2$--0.4, is reviewed. The concept of double exchange is discussed within the general framework of itinerant electron magnetism. The new feature…
A two-site double exchange model with a single polaron is studied using a perturbation expansion based on the modified Lang-Firsov transformation. The antiferromagnetic to ferromagnetic transition and the crossover from small to large…
We study the effects of short-range correlated disorder arising from chemical dopants or local lattice distortions, on the ferromagnetism of 3d double exchange systems. For this, we integrate out the carriers and treat the resulting…
We study the magnetocaloric effect (MCE) in spin clusters of six spins with site spins $s=1$, $3/2$ and $2$ for different exchange anisotropies. We also study MCE in an assembly of spin clusters, on a chain, a 2-D square lattice and 3-D…
We investigate the possible origin of anomalous Hall effect in the CMR (colossal magnetoresistance) materials - the doped rare earth manganites - observed recently by Matl et al. It is demonstrated that the spin-orbit interaction in the…
An introduction is given to the many-body coherent potential approximation (CPA) for the double-exchange (DE) model and the Holstein-DE model, the latter including coupling of the electrons to local phonons as well as to local spins. It is…
By resonant x-ray scattering at the Mn K-edge on La7/8Sr1/8MnO3, we show that an orbital polaron lattice (OPL) develops at the metal-insulator transition of this compound. This orbital reordering explains consistently the unexpected…
Calculations of one-electron spectral functions, optical conductivity and spin-wave energy in the Holstein double-exchange model are made using the many-body coherent potential approximation. Satisfactory agreement is obtained with…
The coupling of magnetic and electronic degrees of freedom to the crystal lattice in the ferromagnetic semimetal EuB$_6$, which exhibits a complex ferromagnetic order and a colossal magnetoresistance (CMR) effect, %, very likely involving…
Polaron and bipolaron formation in the Holstein-Hubbard model with harmonic confinement potential, relevant to quantum dot structures, is investigated in one to three dimensions by means of unbiased quantum Monte Carlo simulations. The…
The metallic or insulating nature of the paramagnetic phase of the colossal-magnetoresistance manganites is investigated via a double exchange Hamiltonian with diagonal disorder. Mobility edge trajectory is determined with the transfer…
The metal-insulator transition in manganites is strongly influenced by the concentration of holes present in the system. Based upon an orbitally degenerate Mott-Hubbard model we analyze two possible localization scenarios to account for…
In doped manganites, the strong electron-phonon coupling due to the Jahn-Teller effect localizes the conduction-band electrons as polarons. This results in polarons are carriers responsible for transport and ferromagnetic ordering rather…
Based on a two-dimensional extended Hubbard model with electron-phonon interaction, we have studied the effect of polaron formation on the charge ordering (CO) transition. It is found that for fully ferromagnetically ordered spins the CO…
We present exact solutions, mainly analytical, for the two-site double-exchange-Holstein model, that allow us to draw a complete picture of the role of both phonon and spin quantum fluctuations in determining the short-range correlations in…
The proximity effect in a model manganite-cuprate system is investigated theoretically. We consider a situation in which spin-polarized electrons in manganite layers antiferromagnetically couple with electrons in cuprate layers as observed…
This work examines the effects of magnetic frustration due to competing ferromagnetic and antiferromagnetic Heisenberg interactions on the spin dynamics of the double-exchange model. When the local moments are non-colinear, a charge-density…