Molecular dynamics simulations of body-centered cubic (bcc) iron thin films with crack defects were carried out by adopting methods of EAM (Embedded Atom Method) potential, spin/exchange potential and spin/neel potential. In this article, the effects of the variation of distance between two crack defects and their directions on the magnetostrictive properties of the thin films are studied, and the corresponding microscopic mechanism is also analyzed. The results show that the defects affect the atomic magnetic moment nearby, and the magnetostrictive properties of thin iron films vary with the direction and spacing of the crack defects. If the defect spacing is constant, the iron model with crack perpendicular to the magnetization direction has stronger magnetostriction than that of parallel to the magnetization direction. The variation of the defect spacing has a great influence on the magnetostrictive properties of the iron model with crack direction parallel to magnetization direction, but it has a small effect on another perpendicular situation. The atoms between the defects may move, but if the defect spacing increases to a certain value, then none of the atoms will move.

Defects are an inevitable occurrence during the manufacturing and use of ferromagnetic materials, making it crucial to study the microscopic mechanism of magnetostrictive properties of ferromagnetic materials with defects. This paper conducts molecular dynamics simulations on low-dimensional iron thin films containing hole or crack defects, analyzes and compares the impact of defect size on magnetostrictive properties, and investigates the microscopic mechanism of their effects. The results indicate that the saturation magnetostrictive strains of the defect models do not increase monotonically as the defect size increases. Additionally, it is discovered that the arrangement of atomic magnetic moments in the initial magnetic moment configuration also affects the magnetostrictive properties. When controlling the size of the hole or crack within a certain defect area, it is found that the hole size has less influence on the initial magnetic moment configuration, resulting in a smaller corresponding change in the saturation strain and thus having a lesser impact on the magnetostrictive properties. Conversely, when the crack size changes, the arrangement of the atomic magnetic moments in the initial magnetic moment configuration changes more significantly, resulting in a greater corresponding change in saturation strain, and thus having a greater impact on the magnetostriction performance.