Transport properties of La0.7R0.3MnO3/SrTiO3/La0.7R0.3MnO3(R=Ca, Sr) magnetic tunnel junctions

Half metals like the doped manganites La0.7Ca0.3MnO3 (LCMO) and La0.7Sr0.3MnO3 (LSMO) are promising candidates for a very large tunneling magnetoresistance (TMR) effect due to their almost 100% spin-polarisation. However, weakening of the magnetic properties at the ferromagnet/insulator interfaces can cause a suppression of the TMR effect in magnetic tunnel junctions (MTJs) made of doped manganites. By introducing a doping profile in LRMO at the interface, the Mn valence can be controlled and the magnetization can be reinforced. We present results on the TMR in planar MTJs grown with different SrTiO3 (STO) barrier thicknesses, as well as with different doping profiles within a few monolayers of LRMO at the interface. The LCMO trilayers were prepared using pulsed laser deposition (PLD) while the LSMO trilayers were grown by molecular beam epitaxy (MBE). The MTJs where investigated in a temperature range T=4.2-300 K and characterized by differential conductance G vs voltage V and resistance R vs H measurements at different bias voltages.