SrMn_(0.5)Fe_(0.5)O_3的自旋玻璃态和过渡金属离子价态的研究

Spin-glass behavior and valence states of transition-metal ions of SrMn_(0.5)Fe_(0.5)O_3

采用固相反应法制备了SrMn0.5Fe0.5O3陶瓷样品,并对样品的晶体结构,磁性和离子价态进行了系统的表征与分析.X射线衍射谱的Rietveld拟合表明样品属于理想的立方钙钛矿型结构,Mn离子和Fe离子随机占据B位的O八面体中心.X射线光电子能谱表明Mn离子为+3和+4的混合原子价态,Fe离子为+3价.样品在大于230K的高温区域呈现Curie顺磁特性,在小于230K的低温区域样品表现出自旋玻璃态行为,这种特性源于Mn离子和Fe离子之间的交换作用及自身价态和分布的不均匀性.由于Fe3+离子占据O八面体的中心,对顺磁区的Mssbauer谱测量表现为四级分裂.

Polycrystalline perovskite SrMn0.5Fe0.5O3has been synthesized by solid state reaction method.The crystal structure,magnetic properties and valence states of Mn and Fe ions have been investigated.X ray diffraction（XRD） and subsequent Rietveld refinement confirmed that SrMn0.5 Fe0.5 O3 is found to be a primitive cubic crystal structure,Mn and Fe atoms randomly occupy the center of oxygen octahedron.Also with the measure of XPS which indicates that Mn ions show trivalent and tetravalent state,while Fe ions are in trivalent state.Paramagnetic phase was observed in high temperature（230 K）,the spin-glass behavior at low temperature（230 K） may caused by the partial ordering of magnetic ions and by the charge disproportion between Mn and Fe ions.The Mssbauer spectra measured in the paramagnetic region exhibit the quadrupole splitting resulting from Fe3＋ ions located in the octahedral sites.