La_(0.7)Ca_(0.3)MnO_3材料中取向畴结构的电镜研究

TEM Study on Structure of Oriented Domains in La_(0.7)Ca_(0.3)MnO_3

利用透射电子显微镜(TEM)及高分辨电子显微镜(HREM)研究了庞磁电阻材料La0.7Ca0.3MnO3(LCMO)中的取向畴结构.电子衍射结果表明,块体LCMO材料中只存在正交相(Pnma),其衍射指数满足消光条件:0kl,k+l=2n+1;hk0,h=2n+1;h00,h=2n+1;0k0,k=2n+1;00l,l=2n+1.在晶粒中可观察到两种典型的取向畴形貌,分别为无定形和楔形.高分辨观察结果还发现,LCMO畴界均为不平直界面,由一些低能量高指数界面组成.

The structure of oriented domains in colossal magneto-resistance material La0.7Ca0.3MnO3 （LCMO） was investigated by transmission electron microscopy（TEM） and high resolution electron microscopy （HREM）.Electron diffraction verified that LCMO presents just a single phase with an orthorhombic symmetry which meets the extinction conditions：0kl,k＋l=2n＋1;hk0,h=2n＋1;h00,h=2n＋1;0k0,k=2n＋1;00l,l=2n＋1,with no other phases observed.The oriented domains in LCMO crystal have two kinds of typical morphologies,i.e.,formless and wedge ones.HREM results showed that the domain boundaries are almost diffuse and consist of some interfaces with low energy and high index.