Strain driven anisotropic magnetoresistance in antiferromagnetic La${}_{0.4}$Sr${}_{0.6}$MnO${}_3$

We investigate the effects of strain on antiferromagntic (AFM) single crystal thin films of La${}_{1-x}$Sr${}_x$MnO${}_3$ (x = 0.6). Nominally unstrained samples have strong magnetoresistance with anisotropic magnetoresistances (AMR) of up to 8%. Compressive strain suppresses magnetoresistance but generates AMR values of up to 63%. Tensile strain presents the only case of a metal-insulator transition and demonstrates a previously unreported AMR behavior. In all three cases, we find evidence of magnetic ordering and no indication of a global ferromagnetic phase transition. These behaviors are attributed to epitaxy induced changes in orbital occupation driving different magnetic ordering types. Our findings suggest that different AFM ordering types have a profound impact on the AMR magnitude and character.