Z. Jirák

Electrical resistivity and thermopower measurements of the hole- and electron-doped cobaltites Ln CoO 3

Two extreme members of the cobaltite series, LaCoO3 and DyCoO3, were investigated by the electrical resistivity and thermopower measurements up to 800-1000 K. Special attention was given to effects of extra holes or electrons, introduced by light doping of Co sites by Mg2+ or Ti4+ ions. The experiments on the La based compounds were complemented with magnetic measurements. The study shows that both kinds of charge carriers induce magnetic states on surrounding CoIII sites and form thus thermally stable polarons of large total spin. Their itinerancy is characterized by low temperature resistivity, which is of Arrhenius type r~exp(EA/kT) for the hole (CoIV) doped samples, while an unusual dependence r~1/Tn (n=8-10) is observed for the electron (CoII) doped samples. At higher temperatures, additional hole carriers are massively populated in the CoIII background, leading to a resistivity drop. This transition become evident at ~300 K and 450 K and culminates at TI-M=540 and 780 K for the La and Dy based samples, respectively. The electronic behaviours of the cobaltites are explained considering two excitation processes in parent compounds. The first one is related to a local excitation from the diamagnetic LS CoIII to close-lying paramagnetic HS CoIII state. Secondarily, a metallic phase of the IS CoIII character is formed through a charge transfer mechanism between LS/HS pairs. The magnetic polarons associated with doped carriers are interpreted as droplets of such IS phase.

Spin state of La Co O 3 : Dependence on Co O 6 octahedra geometry

The electronic structure of the rhombohedral

Magnetic phase diagram of the charge ordered manganite Pr0.8Na0.2MnO3

\mathrm{La}\mathrm{Co}{\mathrm{O}}_{3}

On the magnetic properties of Gd implanted GaN

perovskite is calculated for a number of structures with varying

Ordering phenomena and transport properties of Bi1/2Sr1/2MnO3 single crystals

\mathrm{Co}{\mathrm{O}}_{6}

Canted structures in the Mn3+/Mn4+ perovskites

octahedra geometry. The calculations are based on the generalized gradient approximation (GGA) to the density functional theory and, in order to describe better the strong electron-electron correlation in Co

Structure and physical properties of YCoO{sub 3} at temperatures up to 1000 K

3d

Magnetic and magnetotransport properties of misfit cobaltate Ca3Co3.93O9+δ

states, the

Thermal conductivity and magnetic transitions in Mn3+/Mn4+ manganites

\mathrm{GGA}+\mathrm{U}

Stabilization of the high-spin state of Co3+in LaCo1−xRhxO3

method is employed. Depending on the