Magnetism, Orbital Ordering and Lattice Distortion in Perovskite Transition-Metal Oxides

ChemInform ◽  
2007 ◽  
Vol 38 (47) ◽  
Author(s):  
K. Terakura
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Lattice Distortion ◽  
Orbital Ordering

scholarly journals Nature of novel criticality in ternary transition-metal oxides

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Shapiullah B. Abdulvagidov ◽  
Shamil Z. Djabrailov ◽  
Belal Sh. Abdulvagidov
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Electric Charge ◽  
Critical Exponents ◽  
Transition Metal Oxides ◽  
Lattice Distortion ◽  
Double Exchange ◽  
Metal Cations ◽  
Lattice Energy ◽  
Transition Metal Cations

AbstractThere are the chains of transition-metal cations alternating with the anions of oxygen in ternary transition-metal oxides. When a p-orbital of the oxygen connects the half-filled and empty d-orbitals of adjacent transition-metal cations, double-exchange ferromagnetism takes place. Although double exchange has been well explored, the nature of novel criticality, induced by it, is yet not uncovered. We explored the magnetic-field scaling in the heat capacity of a Sm0.55Sr0.45MnO3 manganite, one of the best ternary transition-metal oxides as it is completely ferromagnetic, and found novel criticality - unordinary critical exponents which are the consequence of coherence of Coulomb lattice distortion and ferromagnetism. The coherence is caused by the trinity of the mass, the charge and the spin of an electron. When the d and p orbitals overlaps, it quickly walks from one site to the another due its lightest mass. And due to its electric charge, it equalizes the valences of the transition-metal cations in the chains and so diminishes the Coulomb lattice distortion. At last, its spin forces magnetic moments of transition-metal cations to ferromagnetically arrange. The disappearance of Coulomb distortions widens the overlap and lowers the elastic lattice energy, so that not only the spin of an electron, but also its electric charge strengthens ferromagnetism. That nonlinear effect strengthens the critical behaviour and critical exponents come off any known universality classes. Thus, the symbiotic coherence of annihilating Coulomb distortions and arising ferromagnetism is a reason of the novel criticality.

scholarly journals ORBITAL INSULATORS AND ORBITAL ORDER–DISORDER INDUCED METAL–INSULATOR TRANSITION IN TRANSITION-METAL OXIDES

2007 ◽  
Vol 21 (05) ◽  
pp. 691-706 ◽  
Author(s):  
DONG-MENG CHEN ◽  
LIANG-JIAN ZOU
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Thermal Fluctuation ◽  
Insulator Transition ◽  
Orbital Ordering ◽  
Excitation Spectra ◽  
Metal Insulator Transition ◽  
Orbital Order ◽  
Metal Insulator

The role of orbital ordering on metal–insulator transition in transition-metal oxides is investigated by the cluster self-consistent field approach in the strong correlation regime. A clear dependence of the insulating gap of single-particle excitation spectra on the orbital order parameter is found. The thermal fluctuation drives the orbital order–disorder transition, diminishes the gap and leads to the metal–insulator transition. The unusual temperature dependence of the orbital polarization in the orbital insulator is also manifested in the resonant X-ray scattering intensity.

Charge and orbital ordering in transition metal oxides

2002 ◽  
Vol 12 (9) ◽  
pp. 257-257
Author(s):  
D. Khomskii
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Degrees Of Freedom ◽  
Relative Role ◽  
Strongly Correlated ◽  
Orbital Ordering ◽  
Spin Orbital ◽  
Electron Phonon Interaction ◽  
Frustrated Systems

Transition metal oxides with strongly correlated d-electrons show an astonishing variety of properties. This is largely determined by an interplay of different degrees of freedom: charge, spin, orbital, lattice ones. Often there appear in them various superstructures. In this talk I will consider different types of superstructures in transition metal oxides, especially charge and orbital ordering, willdiscuss the main mechanisms leading to their formation and consider specific examples of superstructures in manganites, cobaltites and in some frustrated systems. Relative role of purely electronic mechanisms and of the electron-phonon interaction will be discussed. In particular, I will show that the elastic interactions can naturally lead to different superstructures, including stripes. Special features of charge and, especially, orbital ordering in frustrated systems, where frustrations may be caused both by the geometric structure of the lattice and by the special features of orbital interactions, will be considered, and it will be shown that the order-from-disorder mechanism can lead to a unique ordered ground state in many of these cases..

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