Multiferroic properties of Dy modified BiFeO 3 thin films in comparison with Tb modified BiFeO 3 thin films
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R. Anisha and R. Pinto Indian Institute of Technology Bombay, Mumbai 400076, India
S. Bhattacharya Tata Institute of Fundamental Research, Mumbai 400005, India (Received 6 December 2006; accepted 6 March 2007)
Coexistence of ferroelectric and ferromagnetic order parameters was observed at room temperature in Bi0.6Dy0.3La0.1FeO3 thin films grown on Pt/TiO2/SiO2/Si substrates using a pulsed laser deposition technique similar to that for Bi0.6Tb0.3La0.1FeO3. The coexistence of ferroelectric and magnetic domains in specific spatial area of the thin film was also confirmed by scanning probe imaging. As expected, the magnetization values obtained for Bi0.6Dy0.3La0.1FeO3 bulk and thin films were higher than those of Bi0.6Tb0.3La0.1FeO3 bulk and polycrystalline thin films because the magnetic moment of Dy is higher than that of Tb. However, preferentially oriented thin films of Bi0.6Tb0.3La0.1FeO3 exhibit much higher magnetization values. It is speculated that structural alignment caused by stress developed during deposition of these films could be responsible for enhancement in magnetization.
I. INTRODUCTION
Multiferroics are materials that exhibit ferroelectric and magnetic ordering simultaneously in the same phase. If they have a coupling between two order parameters, they have a spontaneous magnetization that can be switched by applying an electric field and spontaneous electric polarization that can be switched by a magnetic field.1 Due to this coupling between ferroelectric and magnetic domains, multiferroics are likely to offer a whole range of novel applications. In addition to their application potential, in recent years their basic scientific aspects have also attracted a great deal of attention. The experimental efforts continue to be focused on investigating new systems exhibiting multiferroic properties at room temperature along with significant magnetoelectric coupling (ME) coefficient. Since then it would only be feasible to make their use in device applications. However, there are very few systems to date that fulfill the requirements.2,3 BiFeO3 is very well-known multiferroic system exhibiting coexistence of antiferromagnetic and ferroelectric ordering at room temperature. Efforts to enhance magnetic and ferroelectric properties of the BiFeO3 system a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0285 2068 J. Mater. Res., Vol. 22, No. 8, Aug 2007 http://journals.cambridge.org Downloaded: 09 Mar 2015
through different possible ways are ongoing. Controlling film growth conditions to put strain on the lattice during film growth has been attempted,4,5 as well as substitution at Bi or Fe sites.6–10 Recently, we were able to demonstrate that bulk as well as thin films of Bi0.9−xTb0.xLa0.1 FeO3 exhibit multiferroic behavior at room temperature on the macroscopic level with significant coupling between two order parameters.11,12 In this paper, we report the results obtained on Dy substituted BiFeO3 (Bi0.6Dy0.3 La0.1FeO3) thin films grown by the pulsed laser depo
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