La_(1/2)Sr_(3/2)MnO_4的制备以及非公度电荷有序和轨道电子有序

Synthesis of and Incommensurate Charge and Orbital Ordering in La_(1/2)Sr_(3/2)MnO_4 Layered Perovskite

用固态反应法制备了La1/2Sr3/2MnO4相.X射线能谱分析证实了样品的平均成分为La0.45Sr1.49-MnO4,且有一定的微观成分不均匀性.用透射电镜在100K低温下观察到了[001]带轴电子衍射花样中出现的超衍射斑点,它来源于非公度电荷有序和轨道电子有序,其非公度调制矢量为k=δ[110]T*,其中δ=0.19.经分析,这种δ=0.19的非公度调制是δ=1/4和δ=1/6的公度调制无规分布的结果.

Polycrystalline bulky samples of La1/2Sr3/2MnO4 were systhesized by conventional solid-state reaction in air. Composition analysis by energy dispersive X-ray spectrometer indicated that the average composition of the sample is La0.45 Sr1.49 MnO4 with a minor fluctuation. The [001] zone-axis electron diffraction patterns taken at about 100 K revealed the presence of superlattice peaks, due to the incommensurate charge and orbital ordering. The incommensurate modulation wave vector is k = δ[110]T*, with δ = 0. 19. Such an incommensurate modulation may be described as a random distribution of two commensurate modulations with δ= 1/4 and 1/6.