NEW AVENUES FOR SPINTRONICS; MAGNETOTRANSPORT IN ULTRATHIN COBALT FILMS ON HEXAGONAL BORON NITRIDE AND FUNCTIONALIZED GRAPHENE

Abstract

This thesis takes a new approach at studying the ferromagnetic Cobalt contacts with a hcp crystal structure commonly used for spintronics devices. By means of different characterization techniques the properties of the FM material and its growth on an atomically flat surface are investigated. The surface is made of hexagonal Boron Nitride (hBN), this is compared to a reference SiO2 substrate. Such techniques are divided into microscopical and electrical characterizations. The first one involves the use of Atomic Force Microscopy and the second a series of Magneto-trasport and Hall magnetometry methods, as well as temperature treatment between 35 K and 300 K. On top of this the device is put through annealing processes. The results give insight on the temperature dependence of the magneto-resistance of the metal on this commonly used substrate and provide indication of a temporary perpendicular preferred anisotropy after annealing treatment. As a related project, the study of the effects of adatom decoration on graphene is also investigated in comparison with the behavior of pristine graphene. This part of the work is dedicated towards further manipulation of graphene in spintronic devices and its possible magnetic properties, these being induced by the magnetic moment formation originated as a consequence of an exchange field. This topic is explored by controlling the density of defects physisorbed on top of graphene and fixed onto it by means of a photochemical reaction using a Raman laser. The techniques used to probe the graphene are charge characterization and spin-transport measurements at room and low temperature while we monitor the evolution of the system. The outcome is the detection of a temperature dependent difference in the diffusion of charge and spin, supporting the idea of inducing magnetic moments in graphene. Both works represent a contribution towards improving the quality of the devices used in spintronics. In particular for the use of future 1-Dimensional ferromagnetic injector and detector contacts.

Date of Award	1 Aug 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Irina Grigorieva (Supervisor) & Ivan Vera Marun (Supervisor)