Magnetic, Electrical Properties And LIV Effects Of Room Temperature Ferromagnetic Sr 4-x R X Co 4 O 10.5 (R=Er, Y) Materials

Cobalt oxide Sr3RCoO4O10.5+?(R= Y or Ln)with conmplex perovskite structure has attracted extensive attention since it exhibits room-tenperature ferromagnetic and unusual doping effects in thermoelectric properties.At present,research on the material system mainly concentrated in Sr3YCo4O10.5+polycrystalline bulk and ferromagnetic mechanism,on the other elements doped and thin film materials are rarely reported.In this thesissy,A-site doped Sr4-xExxCo4O10.5+?polycrystalline bulks and Sr3YCo4O10.5+?epytaxial films were prepared systematically,through XRD,SEM,p-T?S-T?M-Tand M-H measurements,the crystal structure,electrical and magnetic transport properties as well as their corrolations were investigated,and the laser induced voltage(LIV)effect was realized in the tilted films.Sr4-xEjrxCO4O10.5+?(x=0.4,0.6,0.8,0.9,1.0,1.2)polycrystalline bulks were prepared by traditional solid reaction in air with the sintering process of 1180?/24hH+ 1180 ?/24h.The polycrystalline bulks went through a phase transition as the increasing Er doping:when x=0.4 bulks were of cubic phase,when x=0.6 tetragonal superstructure emerged and increased with the increasing of Er doping,when x=0.9-1.0 all the cubic phase had corrpletely transformed to tetragonal phase,when x=1.2 some Er2O3 remained.With the increasing of Er doping,the grain size decreased and the~grain boundaries increased.The polycrystalline bulks exhibited insulating behavior in the range of 90~300 K,the resistivity and the thermal activation energy increased with the increasing Er doping due to the increased grain boundaries and decreased carries concentration.The thermopower decreased with the increasing termperature in the range of 300-650K,and the therropower decreased with the increasing Er doping because of the decreased carries concentration Sr4-xErxCo4O10.5+?(x=0.6?1.2)exhibited room temperature ferromagnetism with Tc=320-335 K,which may derived from the Sr2+/Er3+ ordering and G-type magnetic structure induced unconpensated magnetic moments in CoO4.5+? layers.Sr3YCO4O10.5/LaAlO3(001)thin films with different phase structures were prepared under different laser energy:the films were all of cubic and tetragonal sturctures under higher laser energy(300mJ)and lower laser energy(200mJ).Thin films with cubic phase showed layer+island and island surfice morpholbgies on planar and tilted films,respectively.The films with tetragonal structure exhibited magnetic hysteresis at 4K and 20K,while films with cubic structure exhibited paramagnetism The magnetization of magnetic field along the film surface is lager than magnetic field perpendicular tlhe film surface,which exhibited magnetic anisotropy.The LIV signals were measxured in the films with two phase structures at room temperature.The LIV signals were only obtained in the films with cubic structure,while the LIV signals could not be obtained in the films with tetragonal structure.