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Abstract

Intensive research interests in condensed matter physics have been focused at the strongly correlated electron systems. Recently, tetravalent ions substitution has stimuli much attention as a supplement for the hole-doping. Such electron-doped manganites may be of great potential for the development of all-manganites devices. In this thesis, the field modulation on physical properties in electron/hole-doped manganites films and heterojunctions were investigated. The effects of tetravalent hafnium doping on the structural, transport, and magnetic properties of polycrystalline La_1-xHf_xMnO₃ (LHMO) (0.05 ≤ x ≤ 0.3) were studied systematically. By employing an ultrathin SrTiO₃ buffer layer, manganites could be epitaxially grown on GaAs substrates. The effects of the biaxial strain on the magnetic and electric properties of La_0.9Hf_0.1MnO₃ have been investigated by using 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMN-PT) substrates. Heterojunctions of La_1-xHf_xMnO₃/Nb: SrTiO₃ were fabricated and investigated under different fields (electric, magnetic and optic).