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Nanostructure Effect on Magnetization Processes in FePt Polytwin Crystals
Jingwei Yi1, Xinyu Xu1, Wenqin Yue1
1Department of Materials Science and Engineering, Sichuan University-Pittsburgh Institute, Sichuan University, Chengdu 610065, China.
Abstract:
In FePt polytwin crystals with large magnetocrystalline anisotropy, the boundaries may play a crucial role in the magnetization processes occurring under an external magnetic field. In this study, we employed phase-field modeling and computer simulations to systematically investigate the effect of three types of polytwin boundaries-namely, symmetric (Type I), asymmetric (Type II), and mixed (Type III) boundaries-on magnetization processes as well as coercive fields under an external magnetic field along various directions. Because of the large anisotropy of FePt, the domain wall motion mechanism is usually dominant in the domain switching processes, while the magnetization rotation mechanism only becomes important at the late magnetization stage under a high external magnetic field. Among these three types of polytwin boundaries, the low coercivity is mainly due to the domain wall motion process, which starts from the intersection point at the polytwin boundary. The coercive field for the mixed polytwin boundary (Type III) is always in between the values of Type I and II.
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