This work is focused on the development and the characterization of polycrystalline magnetic tunnel junctions (MTJ) with strontium titanium oxide barrier, SrTiO3, identified as a low band gap tunnel barrier by literature. Such barrier could fulfill the critical application requirement: having a lower resistance area product (RA) in MTJ, or its corollary, having a thicker barrier at constant RA, while keeping the tunnel magnetoresistance ratio (TMR) high enough. Former studies have shown that SrTiO3 deposited by ion beam sputtering (IBS) could crystallize at an unusual low temperature (< 400°C) which could make it compatible with the magnetic layers of MTJs. In a first place, MTJs with a tunnel barrier made of a well known material in spintronics, namely MgO, were deposited. This preliminary work allowed us to highlight the specific parameters affecting the transport properties in MTJs deposited by IBS, including the oxidation type. In a second place, CoFeB/SrTiO3/CoFeB MTJs were developed using IBS and a SrTiO3 ceramic target, learning from our experience on MgO based MTJs. Many combinations of different parameters (including deposition, oxidation and annealing parameters) were explored, leading to two opposite tendencies with systems having either a high TMR (up to 18 %) or a low RA (down to 2.6 Ohm.µm²). SrTiO3 based MTJs were then patterned for the first time and submitted to electrical tests. These tests showed that the MTJs having a low RA exhibited an ohmic behaviour while the MTJs having a large TMR showed the expected tunnel characteristics. Furthermore, the latter MTJs showed an intrinsic dielectric breakdown. In parallel, microstructural characterizations have shown that SrTiO3 based MTJs and MgO based MTJ were alike morphologically. Nevertheless, these observations alone were not enough to assess on the crystalline state of SrTiO3. Many possibilities/tracks aiming at determining the crystallisation temperature of SrTiO3, in the range of extremely low thicknesses used in MTJs, are identified.
