Mechanism of sign crossover of the anisotropic magneto-resistance in La0.7−xPrxCa0.3MnO3 thin films

Abstract

Magneto-resistive anisotropy (AMR) has been studied in 45 nm thick La0.7−xPrxCa0.3MnO3 (LPCMO) manganite films (with Pr doping x between 0 and 0.40) deposited on LaAlO3 (LAO) and SrTiO3 (STO) substrates. The AMR in compressively strained films undergoes a sign change from positive to negative at low temperatures, whereas its sign does not change in films subjected to tensile strain. Temperature dependence of magnetization in a magnetic field applied parallel and perpendicular to the (100)-plane of the films shows that at low temperatures strain-induced rotation of the easy-axis magnetization determines the sign of the AMR. At higher temperatures near the TMI the sign of the AMR is the same in both LPCMO/LAO and LPCMO/STO films, suggesting the dominating influence of percolative transport in the plane of these films at these temperatures.