Angular dependent magnetoresistance (AMR) phenomena in Pr_0.7Ca_0.3MnO₃ film have been investigated. A transition between cos²θ dependent AMR in an insulating state at low fields and sin²θ dependent AMR in a metal state at high fields is observed at intermediate fields, depending on the temperature and/or strength of an applied magnetic field. Although the AMR sign evolution process from cos²θ dependence to sin²θ dependence at low temperature is different from that at high temperature due to existence of ferromagnetic insulator besides charge ordering antiferromagnetic insulator, we believe that such AMR sign evolutions are closely related with magnetic-field-induced ferromagnetic metal percolation behavior.

Angular dependence of AMR(θ) at 150 K and 125 K under different magnetic fields.

Angular dependence of AMR(θ) at 100 K and 75 K under different magnetic fields.