| Nanomaterials, such as nanotube, nanowire, nanocolumn, nanarod and core-shell,have has attracted great attention of researchers with the developing nanotechnology.In addition, they have an importance contribution in the national defense construction,medical drugs and information engineering. The two aspects about nanomaterialshave been studied in this paper. On the one hand, An orientation La0.5Ba0.5MnO3nanocolumn or nanarod on SrTiO3(001) substrate has been grown by hydrothermalmethod. On the other hand, the core-shell BaTiO3/La0.67Sr0.33MnO3nanomaterials hasbeen prepared by sol-gel reaction. Finally, the magnetic and electric property of thesenanomaterials have been researched.1. The magnetic properties of the nanocolumn shows obvious magneticanisotropy by the M-T curve in the perpendicular and parallel to the film. The peaktemperature was181.34K by fitting the coercivity with the different temperature, inaccord with the results of experiments testing. This is further confirmed that themagnetic anisotropy comes from the crystal anisotropy. The magnetic torque showsperfectly periodic cosine function with the different angle in different temperature.The minimum magnetic torque lies in37°and217°and the maximal magnetic torqueappears at140°and320°. Magnetic was further confirmed from the magneticanisotropy of axis.The magnetic anisotropy of nanorod is weaker than that in the nanopillar frommagnetization curves and hysteresis loops. But the magnetic anisotropy increases withthe increasing temperature. We speculate that the change in shape is the main cause inthe nanorod.2. The BaTiO3/La0.67Sr0.33MnO3composite of core-shell structure has beenprepared by sol-gel method, and the concentrations of BaTiO3were10%,20%,30%,40%and50%. BaTiO3is an antiferromagnetic nanomaterial with hexagonal structure,where La0.67Sr0.33MnO3is a ferromagnetic material with orthorhombic structure. Theparticle sizes are about60nm in the two materials. The magnetic and conductivityproperties of the composites are depressed by BaTiO3doping, and the magnetoresistance has been greatly improved because of strong coupling effectsbetween the two phases. For example, at150K the MR values are increased from12.4%(C10) to23.8%(C50). Furthermore, at300K MR values are increased from1.8%(C10) to11%(C50). At50K, the resistance curve presents a butterfly-shapedhysteresis, but the hysteresis disappears at300K. We think that the antiferromagneticcoupling between interfaces of the two phases is the main reason for the resistancehysteresis in C40and C50samples at low temperature. |
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