Artificial Control of Magnetic and Magnetoresistive Properties in the Perovskite Manganites Superlattices and Their Mult
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H.Tabata, K.Ueda, H.Matsui, H.Saeki and T.Kawai The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
ABSTRACT Artificial superlattice of LaFeO 3-LaMnO3 have been formed on SrTiO3(111), (110) and (100) substrates with various stacking periodicity using pulsed laser deposition. Their magnetic properties have been controlled by altering the ordering of magnetic ions (Fe or Mn). Charge disproportionate behaviors are also observed in these superlattices. For the superlattices on (111) plane, all the samples showed ferromagnetic (or ferrimagnetic) behaviors and the same Curie temperature of 230K. In the case of other superlattices formed on (110) and (100), oh the other hand, the increase of the spin frustration effect between LFO-LMO interface with decrease of the stacking periodicity causes reduction of Tc and magnetization. Specially, spin glass like behaviors observed in the superlattices of less than 3/3 stacking periodicity Furthermore, we have constructed heterostructures of Organic/Inorganic multilayers with a sequence of Copper phthalocyanine(CuPc), BaTiO 3 and (LaSr)MnO 3. In this system, magnetoresistant properties have been controlled by the photo irradiation through the lattice strain and/or induced charges caused by the piezo effect and electric field effect. That is magnetoresistance in the (LaSr)MnO3 layer can be controlled by the shining the light. INTRODUCTION Perovskite-type transition metal oxides (ABO 3 ) exhibit various novel properties, such as ferroelectricity, ferromagnetism and high-Tc superconductivity. These materials can be grown layer-by-layer with atomic or molecular layer scale on substrates because they have similar lattice constants. Materials with unique properties are constructed by creating artificial superlattices through the combination of different perovskite-type transition metal oxides. Previously, we demonstrated the creation of new materials that have larger dielectric constants than (Ba, Sr)TiO 3 film by introducing lattice strain at the interface in artificial superlattice made of ferroelectric BaTiO 3 and dielectric SrTiO 3 layers [I]. It is possible to apply the method of creating artificial superlattices to form new magnetic materials with various magnetic structures by combining different magnetic layers. As is demonstrated in this study, materials with various spin structures can be constructed by the method of artificial superlattice with different orientations, making it possible to develop artificially controlled magnetism. We have chosen LaCrO 3-LaFeO 3 and LaMnO3-LaFeO 3 as starting materials. Both
339 Mat. Res. Soc. Symp. Proc. Vol. 602 0 2000 Materials Research Society
LaCrO3 and LaFeO 3 have G-type magnetic structures (inter- and intralayer spin coupling are antiparallel), and their Neel temperatures (TN) are 280K and 750K, respectively (Fig. 1, left) [2-4]. If an artificial superlattice is synthesized by depositing one layer each of LaCrO3 and LaFeO 3 alternately on (111) substrate, it is possi
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