The role of strain in low-field magnetotransport properties of manganite thin films

Abstract

AbstractStrain-induced large low-field magnetoresistance has been observed in very thin Pr0.67Sr0.33MnO3 films1. To better understand the role of strain in the low-field magnetotransport properties of manganite thin films, we have studied and compared very thin (3-20 nm) Pr0.67Sr0.33MnO3 (PSMO), La0.67Ba0.33MnO3 (LBMO), La0.67Sr 0.33MnO3 (LSMO) and La0.67Ca0.33MnO3 (LCMO) films grown on different substrates, such as LaAlO3(001) (LAO), NdGaO3(110) (NGO), and SrTiO3(001) (STO). Due to the lattice mismatch between the films and the substrates ranging from -2.6% to +1%, different strains can be imposed to the films. We have found that: (1) large low-field magnetoresistance(LFMR) behaviors are observed in PSMO, LCMO and LSMO thin films on LAO substrates when a magnetic field is applied perpendicular to the film plane, but the maximum LFMR is the largest in PSMO and LCMO samples; (2) most of the films grown on STO substrates show positive MR when a magnetic field is applied perpendicular to the film plane, and when the field is parallel to the film plane all films show negative MR regardless of the substrates; (3) the large low-field MR is strongly dependent on the film thickness and the composition of the manganites. The anomalous low-field MR effect will be discussed based on strain-induced magnetic anisotropy and domain rotation and movement.