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Studies of electronic charge and spin degrees of freedom in thin films and multilayers of metals and oxides are a promising field of research both at fundamental and applied levels. This new field, also known as spintronics or magnetoelectronics, has revolutionized magnetic recording and computer memory industry. The phenomenon of giant magnetoresistance (GMR) which emerged from such studies has been recognized with a Nobel Prize in 2007. Now-a-days, a relatively new magnetoresistance effect, called the tunnel magnetoresistance (TMR), is at the center stage of spintronics research. However, further advancement of this effect requires design and property optimization of new materials. Doped manganites of the family Re1-xAxMnO3, where Re is rare earth like La, Nd, Pr, etc. and A is divalent alkali such as Ca, Sr, Ba, etc. display a rich variety of phases as a function of temperature, magnetic field, and doping due to the intricate interplay between the charge, spin, orbital, and lattice degrees of freedom. Therefore, it is expected that manganites will play a very crucial role in the development of spintronics research. In this presentation, I will focus on studies of spin-polarized transport in two La0.67Sr0.33MnO3-based thin film structures. The first one consists of plane La0.67Sr0.33MnO3 in its carefully controlled crystallinity and growth orientation, and the issue of interest is the role of grainboundaries on spin-polarized transport. The second one is the layered antiferromagnet La0.45Sr0.55MnO3, whose magnetic and electrical ground states can be tuned by growth related strain. These two systems have been integrated to make a magnetic tunnel junction (MTJ) with cobalt as the other ferromagnetic electrode. The novel aspect of this work is the use of La0.45Sr0.55MnO3 for exchange biasing the ferromagnetic La0.67Sr0.33MnO3. The chemical compatibility and identical lattice parameter of La0.45Sr0.55MnO3 make it ideal for exchange biasing the La0.67Sr0.33MnO3.
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