Structural and magnetic properties of tetragonal and orthorhombic Pr 0.5Sr 0.5MnO 3 thin films

Pr0.5Sr0.5MO3 (PSMO) films with tetragonal and orthorhombic structures were epitaxially grown on a [0 0 1]-oriented LaAlO3 substrate (LAO) and a BaTiO3 substrate (BTO), respectively. It was found that the M(T) curves of the tetragonal PSMO films exhibit one/two distinguished magnetic transition peaks depending on the thickness of the film, which is related to the competition between ferromagnetic (FM) and antiferromagnetic (AFM) interactions in the films. The tetragonal film shows an insulator-to-metal transition (MIT) as well as a metal-to-semiconductor transition with increasing temperature from 10 to 300 K, and the AFM insulating state of the film can be transformed into the metallic state under a magnetic field of 5 T due to the collapse of the AFM insulator state. For the orthorhombic film on BTO substrate, only a FM metallic state is observed without MIT from 10 to 300 K. In addition, a significant colossal magnetoresistance effect is observed with a wide temperature range from T-C (182 K) to 10 K for the tetragonal films, while only around T-C (240 K) for the orthorhombic films.