Chemical pressure effect on optical properties in multiferroic bulk BiFeO <inf>3</inf>

We have investigated diffuse reflectance spectra of the polycrystalline BiFeO 3, Bi 0.9Ba 0.05Ca 0.05FeO 2.95, and Bi 0.9Ca 0.1FeO 2.95 samples to demonstrate crystal-field spectroscopy, which enabled us to explore local distortion in the non-centrosymmetric FeO 6 octahedron, and also to study chemical pressure effect on the band gap and d-d transition band energies. The energy values of band gap and d-d transition bands of the doped BiFeO 3 samples were found to red-shift with the reduced unit cell volume. Absorption spectroscopic studies of the BiFeO 3 samples reveal that nature of the band gap is a direct. Raman spectroscopy study also reveals that the softening/hardening of the certain Raman modes in BiFeO 3 upon substitution of Ca. The chemical pressure induced changes in the band gap and d-d band energies, and the Raman modes of the Ca doped BiFeO 3, which also found to enhance its magnetic and magnetoelectric properties. © 2012 American Institute of Physics.