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A series of Mn-doped TiO_2 nanowires (NWs) were prepared by hydrothermal method at the mole fraction of Mn changing from 0 to 12.0%. X-ray powder diffraction (XRD) analysis shows that all the samples have pure anatase structure. SEM and TEM studies show that the diameter and the length of the Mn-doped TiO_2 NWs are larger than those of the undoped TiO_2 NWs. Energy dispersive X-ray spectroscopy (EDX) reveals that the samples are composed of Ti, Mn and O. According to magnetization measurements, all samples show ferromagnetic behavior, but only the undopedTiO_2 NWs are completely ferromagnetic with a saturated magnetization about 1.0 mA·m~2/kg. Mn-doped TiO_2 samples exhibit antiferromagnetic and ferromagnetic (AF-FM) behaviors simultaneously. Photoluminescence (PL) spectra demonstrate the existence of MnO_2 sublattice. These observations indicate that an AF-WF crossover is induced by the coexistence of TiO_2 sublattice and MnO_2 sublattice. 相似文献
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无位置传感器的无刷直流电机控制技术在变频空调中的应用越来越广泛。在分析了无刷直流电机的无位置传感器矢量控制理论的基础上,提出了一种以XMC1300为控制核心的磁场定向矢量控制方法,并结合一种新的位置观测器检测转子位置,对该方案进行了软件和硬件的设计与实现。实验结果表明,该方法获得了噪音低、效率高、振动小、安全稳定的控制效果,具有重要的实际意义。 相似文献