Sign reversal of anisotropic magnetoresistance in La0.7Ca0.3MnO3/SrTiO3 ultrathin films

We present the observation of strain induced sign reversal of anisotropic magnetoresistance (AMR) in La0.7Ca0.3MnO3 (LCMO) ultrathin films (thickness similar to 4 nm) deposited on SrTiO3 (001) substrate (STO). We have also observed unusually large AMR (similar to 24%) in LCMO/STO thin films with thickness of 6 nm below but close to its Curie temperature (TC) which decreases as the film thickness increases. The sign reversal of AMR (with a maximum value of -6%) with magnetic field or temperature for the 4 nm thin film may be attributed to the increase in tensile strain in the plane of the thin film which in turn facilitates the rotation of the magnetization easy axis. (C) 2014 AIP Publishing LLC.