La0.6Sr0.4MnO3 ramp-edge junctions using (LaAlO3)0.3–(SrAl0.5Ta0.5O3)0.7 barrier

Abstract We have fabricated La 0.6 Sr 0.4 MnO 3 (LSMO)/(LaAlO 3 ) 0.3 –(SrAl 0.5 Ta 0.5 O 3 ) 0.7 (LSAT)/LSMO spin tunnel junctions with a small area by using a ramp-edge geometry. The ramp angle was estimated to be about 25° from measurements of an atomic force microscope. The thickness of a counter LSMO electrode, a bottom LSMO electrode and an insulating LSAT barrier were 100, 200, and 4 nm, respectively. The 1-μm-wide junction showed a tunnel magneto-resistance (TMR) behavior with the TMR ratio of 550% at 100 K. Depending on the directions of the external magnetic field, different TMR characteristics were observed. It may reflect domain structures of the counter and the bottom electrodes, since the ramp-edge junctions are fabricated at the film edges of the base electrode.