title: Effects of site disorder, off-stoichiometry and epitaxial strain on the optical properties of magnetoelectric gallium ferrite.
abstract: We present a combined experimental-theoretical study demonstrating the role of site disorder, off-stoichiometry and strain on the optical properties of magnetoelectric gallium ferrite. Optical properties (bandgap, refractive indices and dielectric constants) were experimentally obtained by performing ellipsometric studies over the energy range 0.8-4.2 eV on pulsed laser deposited epitaxial thin films of stoichiometric gallium ferrite with b-axis orientation and the data were compared with theoretical results. Calculations on the ground state structure show that the optical activity in GaFeO(3) arises primarily from O 2p-Fe 3d transitions. Further, inclusion of site disorder and epitaxial strain in the ground state structure significantly improves the agreement between the theory and the room temperature experimental data substantiating the presence of site disorder in the experimentally derived strained GaFeO(3) films at room temperature. We attribute the modification of the ground state optical behavior upon inclusion of site disorder to the corresponding changes in the electronic band structure, especially in Fe 3d states leading to a lowered bandgap of the material.
authors.affiliation: Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur-208016, India.
authors.forename: Amritendu
authors.initials: A
authors.lastname: Roy
authors.forename: Somdutta
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Surajit
authors.initials: S
authors.lastname: Sarkar
authors.forename: Sushil
authors.initials: S
authors.lastname: Auluck
authors.forename: Rajendra
authors.initials: R
authors.lastname: Prasad
authors.forename: Rajeev
authors.initials: R
authors.lastname: Gupta
authors.forename: Ashish
authors.initials: A
authors.lastname: Garg
mesh_terms: D000465:Algorithms; D002412:Cations; D004581:Electronics; D005290:Ferric Compounds / Q000737:chemistry*; D005708:Gallium / Q000737:chemistry*; D006874:Hydrostatic Pressure; D008280:Magnetics; D015233:Models, Statistical; D055095:Optics and Photonics; D010825:Physics / Q000379:methods; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D002412:Cations; D005290:Ferric Compounds; C001215:ferrite; D005708:Gallium