Electron Transport in Magnetic Tunnel Junctions
Dark, Jason F.
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Electron Transport in Magnetic Tunnel Junctions Jason F. Dark 133 Pages Directed by Dr. Dragomir Davidović In this thesis, I lay the groundwork for studying low temperature magnetization dynamics of ferromagnetic nanoparticles using cryogenic preamplification. The motivation for this work comes from previous measurements by Jiang et al. where spin noise was used for real-time measurement of the magnetization dynamics of a ferromagnetic nanoparticle. I use a high resistance magnetic tunnel junction to model the nanoparticle double junctions and a silicon-germanium heterojunction bipolar transistor as a cryogenic preamplifier. Results of the experiment show an increase in the signal-to-noise ratio and bandwidth of the tunnel magnetoresistance signal produced by the magnetic tunnel junction. I will also discuss preliminary measurements of a double magnetic tunnel junction incorporating a permalloy nanomagnet with and without terbium-doping. Adding small amounts of terbium to permalloy thin films has been shown to increase the dynamical magnetic damping of the thin film. My results show a decrease in the zero bias anomaly in samples with terbium-doping compared to those without terbium-doping.