相关论文: PM-FM transition in a DE model
We explore the derivation of interatomic exchange interactions in ferromagnets within density-functional theory (DFT) and the mapping of DFT results onto a spin Hamiltonian. We delve into the problem of systems comprising atoms with strong…
We report the observation of positive magnetization on field cooling (PMFC) in low applied magnetic fields (H < 100 Oe) in a single crystal of Ca(3)Rh(4)Sn(13) near its superconducting transition temperature (T(c) approx 8.35 K). For 30 Oe…
We study electron-electron interaction effects in the thermodynamic properties of quantum-dot systems. We obtain the direct and exchange contributions to the specific heat C_v in the self-consistent Hartree-Fock approximation at finite…
We study the enhancement of the magnetic transition temperature $T_c$ due to incident light in ferromagnetic semiconductors such as EuS. The photoexcited carriers mediate an extra ferromagnetic interaction due to the coupling with the…
A realistic theory of the quantum paraelectric - ferroelectric transition is presented, involving parameters determined from band calculations and a renormalization group treatment of critical fluctuations. The effects of reduced…
We present a theoretical study of (Ga,Mn)(As,C) diluted magnetic semiconductors with high C acceptor density that combines insights from phenomenological model and microscopic approaches. A tight-binding coherent potential approximation is…
Spin-Fermion systems which obtain their magnetic properties from a system of localized magnetic moments being coupled to conducting electrons are considered. The dynamical degrees of freedom are spin-$s$ operators of localized spins and…
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…
We present a generalization of the spin-fluctuation theory of magnetism which allows us to treat the full rotational invariance of the exchange interaction. The approach is formulated in terms of the local density approximation plus…
The first order antiferromagnetic (AFM) to ferromagnetic (FM) transition in the functional material Fe49(Rh0.93Pd0.07)51 has been studied at low temperatures and high magnetic fields. We have addressed the non-monotonic variation of lower…
The Hubbard model on fcc-type lattices is studied in the dynamical mean-field theory of infinite spatial dimensions. At intermediate interaction strength finite temperature Quantum Monte Carlo calculations yield a second order phase…
A phenomenological theory is suggested to explain the experimentally discovered "paramagnetic peculiarity" and the unconventional change of the energetic state of a layers of high T_{c} of Y-Ba-Cu-O in the vicinity of the phase transition.…
The rate of electron transfer between a molecular species and a metal, each at a different local temperature, is examined theoretically through implementation of a bithermal (characterized by two temperatures) Marcus formalism. Expressions…
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…
A model calculation is presented with the aim to study the interplay between magnetic and structural transitions. The model consists of an orbitally doubly degenerate conduction band and a periodic array of local moments. The band electrons…
From the phase diagram as proposed by Lei et.al., [J. App. Phys 101, 084105 (2007)] a $BaSn_{0.15}Ti_{0.85}O_{3}$ is chosen showing a diffuse phase transition between cubic to rhombohedral (C-R) near room temperature. Dielectric analysis…
We suggest a random field based model for calculation of physical properties of mixed ferroelectric relaxors. Our model naturally incorporates the different orientations of electric dipoles (related to different solid solution components)…
Applying the local density and dynamical mean field approximations to paramagnetic \gamma-iron we revisit the problem of theoretical description of magnetic properties in a wide temperature range. We show that contrary to \alpha-iron, the…
We study heat transfer mediated by near-field fluctuations of the electromagnetic field. In case of metals the latter are dominated by Coulomb interactions between thermal fluctuations of electronic density. We show that an elastic…
Neutron powder diffraction studies of the crystal and magnetic structures of the magnetocaloric compound Mn1.1Fe0.9(P0.8Ge0.2) have been carried out as a function of temperature, applied magnetic field, and pressure. The data reveal that…