Tunneling Magnetoresistance above Room Temperature in La0.7Sr0.3MnO₃/SrTiO₃/La0.7Sr0.3MnO₃Junctions

We have investigated the undesired reduction of spin polarization in La 1- x Sr x MnO 3 (LSMO)/SrTiO 3 (STO)/LSMO spin tunnel junctions by employing superlattices of LSMO/STO with various x of 0.2, 0.3, and 0.4. The systematic data revealed that the instability towards the A-type (layered) antiferromagnetic phase dominates the suppressed ferromagnetism by spin canting in the vicinity of the interface as x increases. Another boundary condition of reduced Curie temperature ( T C ) for x <0.3 gives us a trade-off for the choice of x in spin tunnel junctions. Indeed, atomically regulated LSMO/STO/LSMO tunnel junctions with x =0.3 show tunneling magnetoresistance above room temperature up to 320 K, which agrees well with T C of the superlattices with the same x .