Magnetic localization in mixed-valence manganites

Magnetic localization in mixed-valence manganites

The metal-insulator transition is mixed-valence manganites of the ~La0.7Ca0.3!MnO3 type is ascribed to a modification of the spin-dependent potential JHs–S associated with the onset of magnetic order at TC . Here JH is the on-site Hund’s-rule exchange coupling of an eg electron with s51/2 to the t2g ion core with S 53/2. Above TC, the eg electrons are localized by the random spin-dependent pote...

On the correlation between the X-ray absorption chemical shift and the formal valence state in mixed-valence manganites.

Here the correlation between the chemical shift in X-ray absorption spectroscopy, the geometrical structure and the formal valence state of the Mn atom in mixed-valence manganites are discussed. It is shown that this empirical correlation can be reliably used to determine the formal valence of Mn, using either X-ray absorption spectroscopy or resonant X-ray scattering techniques. The difficulti...

The crucial role of mixed valence in the magnetoresistance properties of manganites and cobaltites.

The mixed valence Mn3+/Mn4+ and Co3+/Co4+ in manganites and cobaltites with the perovskite structure is absolutely necessary for the appearance of magnetotransport properties. It is shown that in these systems the Jahn Teller effect of the transition element, the charge and orbital ordering and the oxygen stoichiometry play a key role in the appearance of large and even colossal magnetoresistan...

Title Magnetic properties of mixed-valence iron phosphate glasses

Charge localization in disordered colossal-magnetoresistance manganites

The metallic or insulating nature of the paramagnetic phase of the colossal-magnetoresistance manganites is investigated via a double-exchange Hamiltonian with diagonal disorder. The mobility edge trajectory is determined with the transfer-matrix method. Density-of-states calculations indicate that random hopping alone is not sufficient to induce Anderson localization at the Fermi level with 20...