Study of Structural and Magnetic Properties Bismuth Ferrite and Substituted Bismuth Ferrites Thin Films Prepared by Spray Pyrolysis Method

Abstract

Functional electronic and magnetic materials are essential in recent times. In the semiconducting and multiferroic period, one aims to develop efficient and smaller materials for storing information, memories, sensors, spintronics devices etc. for the next generation. The number of applications seems to be unlimited in communication technology. Recently, multiferroic has received enormous attention for their unique and strong couplings of electric and magnetic order parameters giving rise to simultaneous ferroelectricity, ferromagnetism, and ferroelasticity. As a result, the multiferroic materials possess a spontaneous polarization, magnetization and piezoelectricity that can be switched on by an applied electric field, a magnetic field, and an elastic force or stress, respectively. These effects allow the construction of novel spintronics devices, spin valves with functionality that is tunable by an electric field, and multi-state memories. Currently studied multiferroics include Bi-based perovskite as BiFeO3, BiMnO3, or BiCrO3. However, most of the existing single-phase multiferroics do not exhibit a magneto-electric effect at room temperature. But, BiFeO3 (BFO) is an intrinsic multiferroic which shows ferroelectricity and antiferromagnetic at room temperature, and thus of strong interest for ambient device applications. BFO has a rhombohedrally-distorted perovskite structure. It shows G-type antiferromagnetic order with a long-periodicity spiral below the Néel temperature (TN = 643K) and ferroelectricity below the Curie temperature (TC = 1103K). The ferroelectricity of BFO is due to the Bi3+ 6s2 lone pair while the weak ferromagnetism results from the residual moment of the canted Fe3+ spin structure. Its G-type antiferromagnetic structure is modulated to a spiral spin structure. This spiral spin structure averages out the net magnetic moment and the induced magnetization. It also inhibits the possibility of measuring the high linear magnetoelectric effect. Substitutions of heterovalent ions to Bi3+ ions destr