Recovery of oscillatory magneto-resistance in phase separated La_(0.3)Pr_(0.4)Ca_(0.3)MnO_3 epitaxial thin films

摘要

In-plane angular dependent magneto-resistance has been studied in La_(.03)Pr_(.04)Ca_(.03)MnO_3 (LPCMO) manganite thin films deposited on the (100) oriented NdGaO_3, and (001) oriented SrTiO_3 and LaAlO_3 substrates. At temperatures where the electronic phase separation is the strongest, a metastable irreversible state exists in the films whose resistivity p attains a large time dependent value. The ρ decreases sharply with an increasing angle θ between the magnetic field and the current, and does not display an expected oscillatory cos~2θ/sin~2θ dependence for all films. The regular oscillations are recovered during repetitive sweeping of 6 between 0° and 180°. We discuss possible factors that could produce these unusual changes in the resistivity.