Anisotropic magnetoresistance in polycrystalline La-0.67(Ca1-xSrx)(0.33)MnO3

We investigated the anisotropic magnetoresistance (AMR) effects in polycrystalline La-0.67(Ca1-xSrx)(0.33)MnO3. An anomalously large AMR of 19.1% was observed near the metal-insulator transition temperature (T-MI) in polycrystalline La0.67Ca0.33MnO3, but slight Sr doping could significantly depress the anomalous AMR around T-MI. By studying the temperature, magnetic field, current direction dependence of AMR and the phase transition process, it was suggested that the anisotropic spin-polarized transport and the demagnetization effect together with the metamagnetic transition around T-MI play important roles in the anomalous AMR effects in polycrystalline perovskite manganites.