Spin Transport In Aluminum Grains and Single Debye Relaxation In BST nanoparticles
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This thesis consists of two distinct components: (1) Spin-polarized electron transport through aluminum array nanoparticles, (2) A single electric relaxation process in Barium Strontium Titanate (BST) nanoparticles. In the first chapter, we summarize our main results and new finding, and we also present our motivation. For the first component (chapters 2-5), we studied electron spin transport in nanometer scale aluminum grains as embedded in a ferromagnet tunneling junction. We observed tunnelling-magnetoresistance (TMR) and spin valve effects. From the TMR strong asymmetry with bias voltage, we explored spin relaxation effects. Additionally we also obtained the spin-coherence time on the order of nanoseconds by using the Hanle effect. For the second component (chapters 6-9), we investigated the dielectric response of BST and Barium Titanate (BTA) (high dielectric constant ferroelectrics) nanoparticles. The results were found to be quite unusual when compared with the dielectric response of film or bulk. The dielectric response is Debye relaxation with only a single relaxation time, and the relaxation time exhibits the Arrhenius Law at temperatures below 200 Kelvin.