Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis The Growth and Characterization of Fe/Tao Multilayers for Spintronics Applications(Izmir Institute of Technology, 2008) Tokuç, Hüseyin; Tarı, Süleyman; Tarı, Süleyman; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn this thesis, the effect of Ta buffer layer and the thickness of the Ta2O5 barrier layer on the structural and magnetic properties of Fe/Ta2O5/Co multilayers have been studied. XRD and AFM techniques were used for structural investigations and VSM was used for investigation of magnetic properties. Refractive index of the barrier layer was determined by ellipsometry technique. In this study, magnetic tunnel junctions have also been fabricated by using photolithography technique and then electrical and magnetoresistance measurements were done.The structural investigations showed that Ta under layer increases the crystalline quality of Fe layer and causes a change on magnetic parameters of Fe films. The AFM results showed that the range of the roughness for all layers is between 1.7 A and 6.3 A. When the thickness of the oxide layer was 4 nm, magnetic decoupling appears. Clear differences between the coercive fields of the ferromagnetic layers were observed in further increase of the barrier layer thickness. The effect of annealing on the Fe/TaOx/Co multilayer was studied and it was found that only the coercivity of Fe film increases with increasing temperature up to the 250C. Then, annealing at 400C showed a sharp decrease in the coercivity of Fe film indicating an intermixing at the interface of Fe/TaOx. Co minor loops showed that the magnetostatic coupling is large for thin barriers and decreases with increasing the barrier thickness. Electrical measurements showed that conduction occurs via tunneling electrons. However, no TMR ratio has been observed after magnetoresistance measurements.Master Thesis Structural and Magnetic Properties Os Si(100)/Ta Multilayers for Spintronics Applications(Izmir Institute of Technology, 2007) Vahaplar, Kadir; Tarı, Süleyman; Tarı, Süleyman; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyThis thesis is concerned with the structural and magnetic properties of Si(100)/Ta/Co single and multilayer thin films grown by DC magnetron sputtering technique. The structural properties of the films have been studied by X-Ray Diffractometer (XRD), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). This study revealed that a single Co film grows amorphous on silicon substrate up to 50 nm at room temperature. After this thickness, Co starts crystallizing in hexagonal (002) plane. The same crystallinity was also observed for 25 nm amorphous Co which was annealed at 4500C at high vacuum for 30 minutes. The presence of a single crystalline tetragonal Ta phase (-Ta) with the orientation along (002) has been observed for 40 nm Ta growth on silicon substrate. The Si(100)/Ta/Co bilayers and multilayers show good crystallinity for both Ta and Co films. SEM and AFM results show that all the single and multilayers grew uniform, continuous and with very low surface roughness. The magnetic properties of the films were investigated using Vibrating Sample Magnetometer (VSM), by measuring hysteresis loops. The effects of the thickness and growth pressure on the magnetic properties of Co films were studied. The easy magnetization axis of the samples is found to be parallel to the Co film plane. As the Co film thickness increased from 4 nm to 15 nm, the coercivity (Hc) decreased from 72 G to 20 G and after a threshold thickness it increased almost linearly up to 180 G for 100 nm film while the magnetization decreased. Moreover, it has been observed that as the Co growth pressure increases, the Hc value of Co films increases. Finally, we obtained two different Hc values for our MTJ sandwich with the structure of Si(100)/Ta/Co/TaOx/Co/Ta.