Magnetic-field-dependent optical studies of Pr0.69Ca0.31MnO3

Abstract We investigated magnetic-field-dependent optical conductivity spectra σ ( ω ) of Pr 0.69 Ca 0.31 MnO 3 at 4.2 K, which was in a charge-ordered insulating state at 0 T. With increasing the magnetic field up to 12 T, we observed an insulator–metal transition around 4 T and large spectral weight changes up to 4 eV. Especially, we found that the spectral weight above 0.5 eV moved to a lower energy region and that a Drude-like peak appeared clearly at 12 T. By analyzing dielectric response changes, we suggested that the field-dependent insulator–metal transition might occur through a percolation process of ferromagnetic metal domains. On the other hand, with decreasing the magnetic field from 12 to 0 T, σ ( ω ) showed little changes, which showed that the ferromagnetic metallic state did not return to the insulating state.