University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Tuesday, December 12th 2017
2:00 pm:
Thesis Defense in PAN 110
Speaker: Ziran Wang, University of Minnesota
Subject: Magnetism for Data Storage: Magnetoresistance Enhancement by Wave Vector Filtering and Transition Shifts in HAMR
This is the public portion of Mr. Wang's thesis defense. His advisor is Randall Victora.

Magnetoresistive heterostructures have important applications in magnetic storage technology and spintronics. This thesis uses Green’s function techniques to calculate the transport properties of a novel structure Fe/Ag/Fe/InAs/Ag. We show that the magnetoresistance can be enhanced to above 1000% due to the wave-vector filtering effect imposed by the InAs layer; meanwhile, the resistance-area product is as low as ~10Ωµm^2. The magnetoresistance shows oscillations with the InAs thickness when the Fermi level is in the conduction band, and the oscillations are quantitatively explained by theory.
Heat-assisted magnetic recording (HAMR) is a leading technology for the next-generation magnetic data storage. This thesis uses micromagnetic simulations to study magnetization transition shifts induced by nonequilibrium spin dynamics in HAMR. We examine the effects of thermal profile, head velocity, damping, and head field rise-time. We also propose methods to determine spin temperature and its lag relative to lattice temperature. By quantifying switching time, spin temperature lag, and superparamagnetic writing, we show that superparamagnetic effects cause largest transition shifts and dominate in typical HAMR processes.

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