相关论文: Phase Diagram in Manganese Oxides
We introduce an effective model for $e_g$ electrons to describe three-dimensional perovskite (La$_{1-x}$Sr$_{x}$MnO$_3$ and La$_{1-x}$Ca$_{x}$MnO$_3$) manganites and study the magnetic and orbital order on $4\times 4\times 4$ cluster using…
The phase diagram of doped manganate compounds La_{1-x}A_xMnO_3 (with divalent A) is studied. We analyze an extension of the double exchange model using the Schwinger boson formalism. Earlier work by de Gennes on the existence of a canted…
The phase diagrams of LaMnO$_3$ perovskites have been intensely studied due to the colossal magnetoresistance (CMR) exhibited by compositions around the $\frac{3}{8}^{th}$ doping level. However, phase segregation between ferromagnetic (FM)…
Phase diagrams in the plane of $r_A$ (the average ionic radius, related to one-electron bandwidth $W$) and $\sigma^2$ (the ionic radius variance, measuring the quenched disorder), or ``bandwidth-disorder phase diagrams'', have been…
A "minimal model" of the Kondo-lattice type is used to describe a competition between the localization and metallicity in doped manganites and related magnetic oxides with Jahn-Teller ions. It is shown that the number of itinerant charge…
The properties of phase-separated systems, e.g. manganites, close to a I order phase transition between charge-ordered insulator and ferromagnetic metal, are usually described by the percolation picture. We argue that the correlated…
We investigate the magnetic phase diagram of the two-dimensional model for e_g electrons which describes layered nickelates. One finds a generic tendency towards magnetic order accompanied by orbital polarization. For two equivalent…
The electronic properties of many transition metal oxide systems require new ideas concerning the behaviour of electrons in solids for their explanation. A recent example, subsequent to that of cuprate superconductors, is of rare earth…
Mesoscopic (500-2000 Angstrom) and microscopic (5-20 Angstrom) phase segregation with temperature and magnetic field was studied in the model manganite Pr0.7Ca0.3MnO3 by high-resolution neutron diffraction and inelastic neutron scattering.…
The roles of crystal-field splitting and Jahn-Teller distortions on the orbital ordering transition are investigated in the single-layer manganites near half doping. Crystal-field splitting of energy levels favoring the $d_{3z^2-r^2}$…
A detailed study of the electric field gradient (EFG) across the Pr1-xCaxMnO3 phase diagram and its temperature dependence is given. Clearly, distinct EFG behaviours for samples outside/inside the charge order (CO) region are observed. The…
The two-orbital model for manganites with both non-cooperative and cooperative Jahn-Teller phonons is studied at hole density x=0.5 using Monte Carlo techniques. The phase diagram is obtained varying the electron-phonon coupling and the…
We present the discovery and refinement by neutron powder diffraction of a new magnetic phase in the Na1-xCaxMn7O12 quadruple perovskite phase diagram, which is the incommensurate analogue of the well-known pseudo-CE phase of the simple…
Disorder on the active d element site is usually very disruptive for conduction and long range order in perovskite transition metal oxides. However, in the background of phase competition such `B site' dopants also act to promote one…
Taking the orbital degeneracy of $e_g$ conduction bands and the Coulomb interaction into account in a double-exchange model, we investigate charge dynamics of perovskite Mn oxides by the Lancz$\ddot{\rm o}$s diagonalization method. In the…
The phase diagram of the multivalent manganites $\rm La_{1-x}Ca_xMnO_3$, in space of temperature and doping $x$, is a challenge for the theoretical physics. It is an important test for the model used to study these compounds and the method…
From a general model of the Mn oxides R_{1-x}A_{x}MnO_3, we derive an effective Hamiltonian in the low-energy subspace using the projection operator method, in which a novel coupling between the spin and orbital degrees of freedom is…
We combine the results of magnetic and transport measurements with Mossbauer spectroscopy and room-temperature diffraction data to construct the magnetic phase diagram of the new family of cubic perovskite manganites SrMn_1-xFe_xO_3. We…
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…
Roles of Coulomb interaction, orbital degeneracy and Jahn-Teller coupling in double-exchange models are examined for Mn perovskite oxides. We study the undoped Mott insulator as well as metal-insulator transitions by hole doping, and…