Antiferromagnetic metallic state and low-temperature magnetoresistance in epitaxial La0.85Sr0.15MnO3 films

We report the magnetic coupling and magneto-transport properties of the epitaxial La0.85Sr0.15MnO3 films, which are fabricated on the (001)-oriented SrTiO3 substrate by RF magnetron sputtering. The anti-ferromagnetism and metallic state were observed in sequence, and both coexist below a critical temperature of 40 K. Meanwhile, the hysteresis loop exhibits the spin-flop transition. The antiferromagnetic phase originates from the A-type spin structure, in which the antiferromagnetic superexchange interaction between the adjacent MnO2 planes is along the c-axis direction. The metallic behavior stems from the double exchange interaction in the MnO2 plane inplane. Furthermore, the spin scattering at phase boundaries between the ferromagnetic and antiferromagnetic phases causes a comparatively large magnetoresistance value of about -30% around 100 K. This effect, together with the colossal magnetoresistance, causes the large magnetoresistance values in a wide temperature range. This work helps to understand the magnetic coupling of the antiferromagnetic metallic state and magneto-transport properties in lightly doped manganite films.