Dynamic properties of phase change in Ge2Sb2Te5 (GST) based nano memory cells & magnetic bubbles in thin film perpendicular anisotropy nanomagnets

Abstract

In this thesis, two di erent technologies with memory applications were studied. The rst one, Phase Change Memory (PCM), is considered a potentially revelation technology for future ultra-high density data storage applications. To visualize the complex nature of the switching dynamics, 3D nite element modeling was carried out in PCM cell based on single layer Ge2Sb2Te5 (GST) alloy, incorporating temperature and phase dependent thermal and electrical conductivities as well as Seeback coe cient to account for the thermoelectric e ect. The experimentally determined resistance maps, those that are indicative of the crystallinity, show good agreement with the simulated phase change behavior con rming the existence of stable intermediate states. The potential stabilization of resistance levels in between the 0 and 1 states enables storage of several data in a single device cell. Current ndings give way to a more stable ultrahigh-density PCM device. The second one is magnetic bubble. The nucleation of stable magnetic bubble in Co/Ni multilayer circular dots and nano-microwires with perpendicular magnetic anisotropy (PMA) and, patterned Spin-Valve are essential for fabrication of new devices for future technologies such as rf oscillator, detector or sensor. The parameters a ecting the formation of bubbles such as the AC in-plane eld demagnetization process, the diameter of dot and the width of wire were investigated. Beside bubble formation in dots, bubble behavior under in-plane magnetic eld, motion induced by current pulses and bubble nucleation in spin-valves were studied.