TECHNICAL: To be able to design and fabricate magnetic elements with controllable magnetization dynamics and switching behaviors are an ultimate goal in the field of magnetism. Through decades of research, progress has been made in dynamics with small angle precession where the assumption of linear response is valid. Magnetization dynamics with large angle precession and switching behaviors remain to be poorly understood, mainly due to the lack of experiment techniques that characterize the damping constant, a critical parameter in magnetization dynamics and switching, at large angle precession with selected spin wave mode, let alone its relationship to structural properties such as shape and composition. To address these properties are essential to understanding the magnetization dynamics accompanied with switching behaviors, leading to high payoff and transformative research. In this SGER, PI will design and implement a sensitive experimental setup to characterize (1) the damping constant at selectable large angle with stable precession and with well defined spin wave modes, (2) magnetization switching behaviors in presence of different microwave frequency and power, and (3) their relationships with structural properties. The research is high risk in nature because of the stringent requirements in the set up sensitivity in order to characterize nanometer thick films of submicron size. The problem may have to be solved by iterative designing and modeling of microwave transmission line along with sample position placement. NON-TECHNICAL: In addition to the high pay-off in scientific understanding of magnetization dynamics accompanied with switching, the high risk undertaking will significantly impact on the recording industries, which are searching for solutions to meet ever increasing storage density demands that have exceeded fundamental physics limits. The research offers microwave assisted magnetization dynamics, solving the conflicting requirements of a small switching field and a long term thermal stability of a magnetic storage bit. The setup can also be expanded to incorporate other existing techniques that can significantly enhance its capability that do not exist currently. Finally, the combination of microwave and spin polarized transport measurements could potentially lead to new phenomena and new types of devices that was not possible before. Such a premise is extremely enticing considering the broad applications in both spintronics and microwave fields. In this regard, training graduate students with expertise in microwave, magnetization, and theoretical model are highly desirable and will be achieved in this proposal.
Key words: Magnetization dynamics, magnetization switching, microwave, microwave wave assisted switching, magnetic domain, ferromagnetic resonance, large angle precession
