中文摘要：

本文通过传统的固相反应法制备了R型六角铁氧体BaFe4-xTi2＋xO11（x=0,0.25,0.5,0.75,1）,并且对它的原子价态以及磁性行为进行了研究. X射线光电子能谱（XPS）结果显示了随着掺杂含量的增加,体系中Fe3＋离子逐渐减少而Fe2＋离子逐渐增加.由于具有非对称结构的阻挫晶格中存在各种关联作用的竞争,使得BaFe4-xTi2＋xO11体系表现出了复杂的磁有序行为,在T 1～250 K和T 2～83 K两处存在磁转变.对这一系列掺杂样品,在相变温度T1之上表现顺磁行为,而在相变温度T2前后的磁化强度都表现出低场下随磁场的增加快速增加,高场下则线性变化且在5x104 Oe时还未达到饱和的行为,表明这一系列掺杂样品是典型的倾斜反铁磁态（canted antiferromagnetic）或者亚铁磁态.

英文摘要：

In this paper, polycrystalline BaFe4-xTi2＋xO11 （x = 0, 0.25, 0.5, 0.75, 1） samples have been synthesized by the conventional solid-state reaction method. X-ray diffraction （XRD） patterns of all the samples show that the diffraction peaks correspond to that of an R-type hexagonal ferrite structure, and no trace of second phase is detected. Measurement of X-ray photoelectron spectroscopy （XPS） reveals that most of the Fe ions in BaFe4Ti2O11 are trivalent and the fitting of two peaks in Fe 2p spectrum corresponding to different Fe ion sites, while the amount of Fe2＋ ions increases with the increase of Ti ions in BaFe4-xTi2＋xO11. The spectroscopy of Ti ions confirms that the valence of Ti in BaFe4-xTi2＋xO11 are tetravalent. Magnetic susceptibility of BaFe4-xTi2＋xO11 （x=0, 0.25, 0.5, 0.75, 1） reveals two magnetic transitions at T 1～250 K and T 2～83 K, which indicate a complex magnetic order driven by competing interactions on a frustrated lattice with a noncentrosymmetric structure. For all the samples, the magnetic susceptibility obeys Curie-Weiss law above T 1, and M-H curves exhibit a linear variation with magnetic field in this temperature range, which is consistent with the paramagnetic behavior. A decrease of the effective magnetic moment is due to the increase of Fe2＋ ions with the increase of Ti content in BaFe4-xTi2＋xO11. Below T 1, the magnetization curve as a function of temperature （M-T ） and the magnetization versus magnetic field （M-H） at different temperatures imply its characteristic of a typical canted antiferromagnetic or ferrimagnetic state. Meanwhile, the transition temperature T 2 drops gradually with the increase in Ti content, which might be related to the change of occupying of Fe ions in the kagome layers.