Abstract:
In this dissertation, thin films of two promising rutile oxide materials (CrO<sub>2</sub> and VO<sub>2</sub>) are studied. Additionally, magnetic tunnel junctions (MTJs) with these two materials as ferromagnetic (CrO<sub>2</sub>) and barrier layer(VO<sub>2</sub>) are fabricated and their properties are investigated. The CrO<sub>2</sub> thin films are successfully grown on TiO<sub>2</sub> (001) substrates by atmospheric pressure chemical vapor deposition (APCVD). Their structural and magnetic properties have been examined. The Stoner-Wohlfarth model is used to extract the distribution of the effective anisotropy field in the CrO<sub>2</sub> (001) films for providing a better understanding of the out-of-plane magnetic behavior. The unexpected in-plane magnetic behavior is explained by the possible existence of stripe or vortex domain structures in the films. Besides CrO<sub>2</sub>, VO<sub>2</sub> thin films and CrO<sub>2</sub>/VO<sub>2</sub> heterostructures have been grown on TiO<sub>2</sub> substrates of different orientations - (100), (110) and (001) - and their electrical and magnetic properties are studied. Finally, MTJs with CrO<sub>2</sub> as the ferromagnetic electrode, heteroepitaxial VO<sub>2</sub> as the barrier layer, and Co as the counter electrode are fabricated, and their transport and magnetic properties are investigated. The bias, temperature and barrier thickness dependence of the tunneling magnetoresistance (TMR) of these CrO<sub>2</sub>/VO<sub>2</sub>-based MTJs are presented. The Simmons and Brinkman models are used to estimate the barrier height of the tunneling device. In addition, the magnetic behavior of the MTJs at different temperatures is studied.
