Raman spectroscopy and magnetoelectric properties of laser ablated La and Cr doped BiFeO3 thin films

Abstract

Epitaxial thin films of multiferroics Bi1-xLaxO3 (x = 0.0, 0.05, 0.10, 0.15 and 0.20)and BiFe1-xCrxO3.....(x = 0.05, 0.10, 0.15 and 0.20) were grown on SrTiO3(100) and (110) substrates by pulsed laser deposition (PLD). X-ray diffraction (XRD)U was used to study the structure, orientation, and crystallinity of the film. The growth mechanism and microstructure of the films were studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The magnetic properties (magnetization vs. temperature and M-H loops) of the films were carried out using a superconducting quantum interference device (SQUID)magnetometer and the electrcal properties (dielectric permittivity and leakage current) of the films were carried out using our in-house characterization facilities. The polarized Raman scattering was used to identify and understand the phonon vibrations and crystalstructure of the films. It is found that the films grown on STO(100) and (110) substrates are of monoclinic, contrary to the reported bulk-like rhombohedral and tetragonal structure. The temperature variation of Raman scattering was investigated to understand the dynamicc of the phase transitions (magnetic and ferroelectric). We observed phonon-magnon coupling near the magnetic transition (370 C) and a structural phase transition at 810C. The result will be discussed in details.