UCLA

Magnetism has been utilized since ancient civilizations to build tools for day to day life for example, magnetic compass. Understanding of nature behind magnets has ever since evolved passing significant milestones such as, discovery of interplay between magnetism and electricity leading to invention of electric motor and dynamo and, microscopic insight developed following discovery of quantum mechanics. About twenty years ago we passed arguably the most recent milestone with the prediction of the ability to manipulate a nano sized magnet with the aid of the spin of an electronic current. With the advent of magnetic tunnel junctions (MTJ), one of the main applications of this has been spin transfer torque nano oscillators (STNO) that have attracted great attention. Recently, a new emerging field regarding magnetic skyrmions in MTJs has shown even more promising aspects such as higher energy efficiency for real world applications. In the first half of this thesis, we present a tri- layer MTJ based STNO offering 6 GHz microwave emission for both current polarities at zero external magnetic field which is the highest frequency achieved in absence of any bias field to-date, to the best of our knowledge. We have investigated into spin dynamics of this STNO discussing about out of plane (OOP) precessions along with micromagnetic simulations. In the second half of this thesis, we present observation of skyrmionic signature in an MTJ at cryogenic temperature producing random telegraph signal (RTS). We have studied the dependencies of this RTS upon various physical parameters. RTS seen in MTJs involving ferromagnetic states has attracted attention in the research community as it is an ideal candidate to realize neuromorphic computers which are inspired on human brain offering tremendous improved performance in specific tasks over conventional boolean computing. We believe this investigation into RTS involving skyrmionic states in an MTJ will further electrify this on going expedition.