Nanorods of Dy Modified BiFeO 3 for Multifunctional Device Applications
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Nanorods of Dy Modified BiFeO3 for Multifunctional Device Applications M. Mandal, S. P. Duttagupta, V. R. Palkar Electrical Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra, India. ABSTRACT We have developed material (Bi0.7Dy0.3FeO3)(BDFO) which exhibits the multiferroic behavior at room temperature with significant coupling in bulk as well as thin films. If these properties could be fashioned in nano rods, implementation in devices could be certainly more prominent and straight forward. We have therefore used vertically aligned arrays of silicon rods (~5 μm in length and ~ 500 nm in diameter) as base material to direct the growth of BDFO in rod form. BDFO is deposited on the surface of Si rods by using pulsed laser deposition technique. These BDFO/Si rods are then separated from the support, dispersed into propanol and transferred onto SiO2/Si substrates for testing. X-ray diffraction (XRD) results indicate presence of phase pure BDFO layer on Si rods. Saturation observed at room temperature in magnetic and ferroelectric hysteresis loops confirm the coexistence of ferromagnetic and ferroelectric properties. Change in ferroelectric polarization measured on single rod in the presence of applied magnetic field suggests the coupling behavior between two order parameters. Moreover, change in magnetic domain pattern of BDFO rods associated with applied electric field further supports the presence of coupling behavior in both ways. The vertical and lateral displacement occurring in BDFO/Si rods with applied electric field helps to confirm their piezoresponce behavior. BDFO/Si nanorods with multifunctional properties could find variety of novel device applications with flexibility and simplicity in operation. It might include single rod power generation by means of applied stress or magnetic field. INTRODUCTION Multiferroic systems, which exhibit coexistence of both ferroelectric and ferromagnetic ordering at room temperature, are of great importance for a variety of device applications, Due to coupling between two order parameters, it is possible to bring polarization in the multiferroic system by either means (applying electric and magnetic field). We have been successful in developing Bi0.7Dy0.3FeO3 (BDFO) material which exhibits the multiferroic behavior at room temperature with significant coupling in bulk as well as thin films grown directly on Si substrate [1]. However, if multiferroic sample could be fashioned as nanorods, implementation in devices could be much straight forward. Unfortunately, BDFO is difficult to bring in nanorod form by chemical synthesis or porous template directed methods, mainly because of complexities associated with precise control of elemental composition and avoidance of phase separation. To overcome this problem, we use vertically aligned arrays of Si nanorods and direct the growth of a uniform layer of the BDFO on the surface of these rods by using pulsed laser deposition technique. The coating method of choice was pulse laser deposition (PLD), because of its well
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