The values and signs of the contributions to superexchange interaction Co 3+ ions in LaCoO 3 different spin states, namely, a pair intermediate (IS) state ions, one which is other high-spin (HS) state, are studied. For this purpose, virtual electron-hole pairs produced course (the so-called exchange loops) have been studied within framework multiband generalization Hubbard model. It shown that ...

In systems with strong electron-lattice coupling, such as manganites, orbital degeneracy is lifted, causing a null expectation value of the orbital magnetic moment. Magnetic structure is thus determined by spin-spin superexchange. In titanates, however, with much smaller Jahn-Teller distortions, orbital degeneracy might allow non-zero values of the orbital magnetic moment, and novel forms of fe...

A systematic inelastic neutron scattering study of the superexchange interaction in three different undoped monolayer cuprates (La2CuO4, Nd2CuO4 and Pr2CuO4) has been performed using conventional triple axis technique. We deduce the in-plane antiferromagnetic (AF) superexchange coupling J which actually presents no simple relation versus crystallographic parameters. The absolute spectral weight...

We study the crossover from the underdoped to the overdoped regime of the t-J model within a plaquette dynamical mean field approach. We find that the shortest electron lifetime occurs near optimal doping where the superconducting critical temperature is maximal. The mean field theory provides a simple physical picture of this effect. In the underdoped regime, the charge carriers propagate cohe...

We present a systematic study of the ferromagnetic transition induced by the holes in nitrogen doped Zn12xMnxTe epitaxial layers, with particular emphasis on the values of the Curie-Weiss temperature as a function of the carrier and spin concentrations. The data are obtained from thorough analyses of the results of magnetization, magnetoresistance, and spin-dependent Hall effect measurements. T...