Low-field magnetoresistance anisotropy in ultrathin Pr0.67Sr0.33MnO3 films grown on different substrates

We have conducted a comparative study of the strain effect on the anisotropic low-field magnetoresistance (LFMR) in ultrathin ${\mathrm{Pr}}_{\mathrm{0.67}}{\mathrm{Sr}}_{\mathrm{0.33}}{\mathrm{MnO}}_{\mathrm{3}}$ films epitaxially grown on ${\mathrm{LaAlO}}_{\mathrm{3}}\mathrm{(LAO)},$ ${\mathrm{NdGaO}}_{\mathrm{3}}\mathrm{(NGO)},$ and ${\mathrm{SrTiO}}_{\mathrm{3}}\mathrm{(STO)}$ substrates. Distinctive LFMR effects have been observed on films with compressive (on LAO), tensile (on STO), and nearly zero (on NGO) strains. The films with compressive strain show very large negative LFMR and MR hysteresis when a magnetic field is applied perpendicular to the film plane, while those with tensile strain show positive LFMR for the same field orientation. All samples show negative MR in a parallel magnetic field. These results can be qualitatively interpreted based on the strain-induced magnetic anisotropy.