Irreversible photoinduced insulator-metal transition has been observed in a perovskite manganite doped with monovalent Na+, Pr 0.75Na0.25MnO3. The increase of the conductance is estimated to be of the order of 104-105, considering the shallow penetration depth (∼0.1 μm) of illumination light. Analysis of the dc- and ac-susceptibility data shows that the system is in a cluster glass state below 45K, which means that ferromagnetic metallic clusters exist in insulating matrix. The photo-excitation helps the clusters to dislodge from a local energy minimum and to seek more stable configuration. The observed large increase of the conductivity can be well explained by the percolative conduction. We argue that metastability is due to the large charge mismatch between the monovalent Na+ ion and trivalent Pr3+ ion or the deviation of the average Mn valency from 3.5+.
All Science Journal Classification (ASJC) codes
- Materials Science(all)