Observation of nano-scale magnetic domains in Sr2FeMoO6 using lorentz transmission electron microscopy

Abstract

The Sr2FeMoO6 (SFMO) is crystallized in a double perovskite (DP) structure. The DP structure is composed of two different metal cations at B site in perovskite structure (ABO3). Antiferromagnetic superex-change occurs through the p orbital of neighboring anion, because the distance between metal cations is long. This superexchange leads to ferromagnetism of SFMO. This magnetic material has higher Curie temperature and magnetoresistance than those of mixed-valence manganite. Furthermore, SFMO is most popular half-metallic material with the potential for magnetoelectronic applications. In this research, SFMO synthesized by solid state reaction was characterized by X-ray diffraction and vibrating sample magnetometer for analyzing its phase and magnetic properties, respectively. In order to observe the magnetic domain structure and microstructure of SFMO, conventional transmission electron microscopy (TEM) and Lorentz microscopy were used. Lorentz microscopy does not use objective lens which strongly magnetize specimen to one direction. Therefore, it can easily observe minute magnetic domain. Using Fresnel imaging mode, which is controlling defocus from under- to over-focus, few images could be obtained. These images were shown by contrast inversion resulting from change of electron intensity. Program using transport intensity equation was used to quantify and observe magnetization distribution. As a result, nano-scale magnetic domains of SFMO were firstly observed.