Mechanically coupled phase field modeling of ferromagnetics unter thermal fluctuation

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Magnetic moment is sensitive to thermal fluctuation, which leads to strongly effect on magnetization switching dynamics, domain evolution and coercivity. Moreover, mechanically controlled/assisted magnetization switching appears as an attractive alternative method to achieve a deterministic 180 degree switching in new memory cell designs. Thermal fluctuation plays an important role in the mechanically-coupled switching mechanism. In this project we will first develop a theoretical framework and numerical strategies to study the influence of thermal fluctuation on switching dynamics, domain evolution and coercivity in ferromagnetics at finite temperature below the Curie temperature, with the consideration of coupling with mechanics. Particularly, a phase field model will be derived from a thermodynamic framework with the microforce (configurational force) theory, in which thermal fluctuation induced random fields will be treated in the microforce balance. The developed model will be implemented with the stochastic finite element method (SFEM), by using efficient numerical strategies. Comprehensive simulations will be carried out in order to evaluate the effect of thermal fluctuations on the magnetization switching dynamics, domain structure evolution and coercivity. Through the proposed theoretical study and numerical simulations, the interaction of magnetization with thermal fluctuations and mechanical field will be disclosed. This project should provide a novel toolkit, which is useful not only for the study and design of next generation of nanoferromagnet-based memory and logic devices, but also for revealing the coercivity mechanism of high temperature magnets such as NdFeB.