TEM study of remnant domain state correlation to relaxation rate and vortex nucleation barrier measurements in patterned Permalloy elements
Much of the advancements in our information technology depend on the understanding of magnetization reversal dynamics in patterned ferromagnetic thin-film systems. In situ Magnetic domain responses to an applied field are studied with transmission electron microscopy (TEM). While micromagnetics simulators can correctly locate low-energy states as well as the probable paths to reach them, they do not calculate the energy barriers associated with such transitions. Combining Lorentz microscopy with micromagnetics simulations, not only are the exact reversal mechanisms determined, but also revealed is the role that the external field plays in a fundamental magnetization reversal mechanism: vortex nucleation. Based on a statistical collection of temperature and field varying, time-sequenced TEM micrographs, measurements of nucleation barrier as a function of different holding fields are made. Existing theories and empirical formulation are in agreement with our measurements.
Presented by: June W. Lau
Mentor: Robert McMichael
Mail stop: 8552
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