| Strongly correlated electron systems, especially perovskite type of manganites, in which the electronic transport properties of transition metal oxides strongly interact with the magnetic properties and with the crystal lattice, are of great interest not only due to their application in technology but also to the need of fundamental research in understanding the origin of the large magnetoresistance. In most cases, a relatively small change of chemical composition or temperature drives some dramatic phase changes.; In order to understand the structural related magnetic and transport properties of substituted perovskites La0.7Sr0.3MnO3 (LSMO), we studied the effects of replacing some of the Mn with Ti, Zr, and Cu atoms. The structural, magnetic and electrical phase transitions and transport properties of these compounds were investigated by neutron diffraction, magnetization, electric resistivity, and in addition for Cu, theoretical band structure calculations.; These abnormal behaviors relative to the parent manganite perovskite are explained by the competition between the double exchange and super exchange interactions, local Jahn-Teller distortion, the dilution of magnetic ordering by the formation of AF clusters, the change of electron carrier density and band structure, and complex interactions between electrons, phonons, and polarons. |
