相关论文: Percolative conductivity and critical exponents in…
The superconducting transition in presence of strong columnar disorder parallel to the magnetic field is considered. A solvable model appropriate for description of the broad crossover regime towards the true "glassy" critical behavior is…
A La0.75Ca0.25MnO3-film grown by metalorganic aerosol deposition technique was investigated by scanning tunnelling microscopy and spectroscopy. A small spot was found on the surface which exhibits the expected magnetic field dependence of…
Optical conductivity data s(w) of the colossal magneto-resistance (CMR) pyrochlore Tl2Mn2O7 are presented as functions of temperature (T) and externalmagnetic field (B). Upon cooling and upon applying B near the Curietemperature, where the…
The effect of low magnetic fields on the transport properties of a manganite compound with magnetic phase separation is studied. The different behavior obtained in samples of La0.5Ca0.5MnO3 related to the way in which the low field is…
Pairing of oxygen holes into heavy bipolarons in the paramagnetic phase and their magnetic pair-breaking in the ferromagnetic phase [the so-called current-carrier density collapse (CCDC)] has accounted for the first-order ferromagnetic…
In this paper we critically discuss several examples of two-dimensional electronic systems displaying interaction-driven metal-insulator transitions of the Mott (or Wigner--Mott) type, including dilute two-dimension electron gases (2DEG) in…
Quantum transitions between the Mott insulator and metals by controlling filling in two-dimensional square lattice are characterized by a large dynamical exponent $z=4$ where the origin of unusual metallic properties near the Mott insulator…
Variation of magnetocaloric (MC) effects has been systematically investigated for colossal magnetoresistive (CMR) manganites R0.6Sr0.4MnO3 (R=La-Gd). As the one-electron bandwidth is reduced, the temperature profile of MC effect, i.e.,…
Recent measurements of the magnetoresistance (MR) of amorphous superconducting thin films in tilted magnetic fields have displayed several surprising experimental details, in particular a strong dependence of the MR on field angle at low…
In composite materials composed of soft polymer matrix and stiff, high-aspect-ratio particles, the composite undergoes a transition in mechanical strength when the inclusion phase surpasses a critical density. This phenomenon (rheological…
A recently developed self-consistent effective medium approximation, for composites with a columnar microstructure, is applied to such a three-constituent mixture of isotropic normal conductor, perfect insulator, and perfect conductor,…
The one-orbital model for manganites with cooperative phonons and superexchange coupling $J_{\rm AF}$ has been investigated via large-scale Monte Carlo (MC) simulations. Results for two-orbitals are also briefly discussed. Focusing on…
We study a continuous quasi-two-dimensional order-disorder phase transition that occurs in a simple model of a material that is inhomogeneously strained due to the presence of dislocation lines. Performing Monte Carlo simulations of…
The frequency and temperature dependence of the optical conductivity of ferromagnetic manganites is explained within the framework of the bipolaron theory. As these materials are cooled below the Curie temperature, the colossal…
In view of recent experiments, indicating the spatial coexistence of conducting and insulating regions in the ferromagnetic metallic phase of doped manganites, we propose a refined mixed-phase description. The model is based on the…
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…
Magnetoconductivity of the disordered two- and three-dimensional superconductors is addressed at the onset of superconducting transition. In this regime transport is dominated by the fluctuation effects and we account for the interaction…
Hall resistivity and magneto-thermopower have been measured for colossal magnetoresistive Tl2Mn2O7 over wide temperature and magnetic-field ranges. These measurements revealed that a small number of free electron-like carriers is…
Of the perovskites, ABX_<3>, a subset of special interest is the family in which the A site is occupied by a lanthanide ion, the B site by a rare earth and X is oxygen, as such materials often exhibit a large change in electrical resistance…
We argue that colossal magnetoresistance is a critical phenomenon and propose a mechanism to describe it. The mechanism relies on the halfmetallic behavior of the materials showing colossal magnetoresistance, and yields a correlated…