Role of strain in magnetotransport properties of Pr_0.67Sr_0.33MnO₃ thin films

We have studied the strain effects on the structural and magnetotransport properties of Pr_0.67Sr_0.33MnO₃ (PSMO) thin films. The PSMO films were epitaxially grown on LaAlO₃ (001), SrTiO₃ (001), and NdGaO₃ (110) substrates that induce biaxial compressive, tensile, and almost no strain in the films, respectively. The film thickness t, varied between 4-400 nm, was used as another controlling parameter of strain for each type of film. There exist two distinct thickness ranges with different thickness dependence of the magnetotransport properties. For t<20 nm, the zero-field resistance peak temperature (T_p) and the high-field magnetoresistance (HFMR) properties are critically dependent on the thickness and the substrate. For t>20 nm, the T_p and the HFMR ratio show weak t dependence. The results show evidence for the effects of the Jahn-Teller type distortion as well as disorders on the resistive transition temperature and the HFMR.