Related papers: Ground-State Magnetization in Disordered Systems :…
We shed light on the interplay between structure and many-body effects relevant for itinerant ferromagnetism in LaAlO$_3$/SrTiO$_3$ heterostructures. The realistic correlated electronic structure is studied by means of the (spin-polarized)…
The magnetic excitations of the double exchange (DE) model are usually discussed in terms of an equivalent ferromagnetic Heisenberg model. However this equivalence is valid only at a quasi--classical level - we show that both quantum and…
As discussed in this chapter, we develop a mean-field mathematical method to calculate the ground states of antiferromagnets and better understand the applied magnetic-field induced exotic properties. Within antiferromagnetic materials…
We investigate the spin-ordered states in multilayer massless Dirac fermion systems under magnetic fields, in which the intralayer interaction is ferromagnetic owing to the exchange interaction, while the interlayer interaction is…
We study a parametrically modulated oscillator that has two stable states of vibrations at half the modulation frequency $\omega_F$. Fluctuations of the oscillator lead to interstate switching. A comparatively weak additional field can…
Using a Hartree-Fock mesh method and a configuration interaction approach based on a generalized Gaussian basis set we investigate the behaviour of the exchange and correlation energies of small atoms and molecules, namely th e helium and…
Fluctuation relations are derived in systems where the spin degree of freedom and magnetic interactions play a crucial role. The form of the non-equilibrium fluctuation theorems relies in the assumption of a local balance condition. We…
It is shown that site disorder induces noncoplanar states, competing with the thermal selection of coplanar states, in the nearest neighbor, classical kagome Heisenberg antiferromagnet (AFM). For weak disorder, it is found that the ground…
We investigate the influence of an interband exchange interaction on magnetism in a two-band Hubbard model. Our main emphasis lies on spin-flip scattering which is often neglected but is neccessary to retain the full rotational symmetry of…
We introduce a new coarse grain model capable of describing the phase behavior of two dimensional ferromagnetic systems with competing exchange and dipolar interactions, as well as an external magnetic field. An improved expression for the…
We have analyzed the magnetic interactions of a five orbital model for iron superconductors treated both within Hartree-Fock and Heisenberg approximations. We have found that the exchange constants depend non-trivially on the Fe-As-Fe angle…
A modification of the ground state of the classical-spin Heisenberg Hamiltonian in the presence of a weak superstructural distortion of an otherwise Bravais lattice is examined. It is shown that a slight modulation of the crystal lattice…
The effects of interactions in a 2D electron system in a strong magnetic field of two degenerate Landau levels with opposite spins and at filling factors 1/2 are studied. Using the Chern-Simons gauge transformation, the system is mapped to…
We present results of a numerical mean field treatment of interacting spins and carriers in doped diluted magnetic semiconductors, which takes into account the positional disorder present in these alloy systems. Disorder is found to enhance…
We review the effects of electron-electron interactions on the ground-state spin and the transport properties of ultra-small chaotic metallic grains. Our studies are based on an effective Hamiltonian that combines a superconducting BCS-like…
A hybrid spin-electron system on one-dimensional tetrahedral chain, in which the localized Ising spin regularly alternates with the mobile electron delocalized over three lattice sites, is exactly investigated using the generalized…
We present a theoretical study of the the effects of off-resonant polarized optical fields on a ferromagnetic model system. We determine the light-induced dynamics of itinerant carriers in a system that includes magnetism at the mean-field…
We study the ground state of a $d$--dimensional Ising model with both long range (dipole--like) and nearest neighbor ferromagnetic (FM) interactions. The long range interaction is equal to $r^{-p}$, $p>d$, while the FM interaction has…
We demonstrate that the magnetization in magnetic semiconductors exhibits nutational motion when subjected to an external magnetic field. This behavior originates from the splitting of the conduction-electron band which induces anisotropic,…
Dipole-dipole interactions in a square planar array of sub-micron magnetic disks (magnetic dots) have been studied theoretically. Under a normal magnetic field the ground-state of the array undergoes many structural transitions between the…