Dielectric properties characterization of La- and Dy-doped BiFeO 3 thin films
- PDF / 338,332 Bytes
- 6 Pages / 585 x 783 pts Page_size
- 86 Downloads / 252 Views
Vaijayanti R. Palkar Tata Institute of Fundamental Research, Mumbai 400005, India
Alexander K Tagantsev Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne CH-1015, Switzerland
Hsin-I Chien London South Bank University, London SE1 0AA, United Kingdom
K. Prashanthi Indian Institute of Technology Bombay, Mumbai 400076, India
Anna-Karin Axelsson Imperial College, London SW7 2AZ, United Kingdom
S. Bhattacharya Tata Institute of Fundamental Research, Mumbai 400005, India
Neil McN Alford Imperial College, London SW7 2AZ, United Kingdom (Received 3 January 2007; accepted 22 May 2007)
The dielectric response of La- and Dy- doped BiFeO3 thin films at microwave frequencies (up to 12 GHz) has been monitored as a function of frequency, direct current (dc) electric field, and magnetic field in a temperature range from 25 to 300 °C. Both the real and imaginary parts of the response have been found to be non-monotonic (oscillating) functions of measuring frequency. These oscillations are not particularly sensitive to a dc electric field; however, they are substantially dampened by a magnetic field. The same effect has been observed when the volume of the characterized sample is increased. This phenomenon is attributed to the presence of a limited number of structural features with a resonance type response. The exact origin of these features is unknown at present. Leakage current investigations were performed on the whole set of films. The films were highly resistive with low leakage current, thereby giving us confidence in the microwave measurements. These typically revealed ‘N’-type I-V characteristics.
I. INTRODUCTION
Multiferroic (MF) materials are those in which more than one ferroic order (magnetic, electric, elastic) coexists and is coupled.1 The possibility of including extra functionality with a device makes MF materials very attractive for application in microwave technology. However, there are no (or very few) papers reporting the properties of MF materials at frequencies higher than a few megahertz. The main reason for the lack of published high-frequency [radio frequency (rf) and microwave]
a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0287 J. Mater. Res., Vol. 22, No. 8, Aug 2007
http://journals.cambridge.org
Downloaded: 28 May 2014
measurement data is the high leakage current in these materials and especially in samples of thin films. BiFeO3 (BFO) is one of the very few single-phase multiferroic materials and is the subject of increased scientific interest.2–4 The challenges with BiFeO3 (BFO) arise from its large leakage current4 and from the fact that at room temperatures bulk BFO is ferroelectric and antiferromagnetic.3 Doping of BFO with Dy and La helps in the stabilization of the perovskite phase and in the reduction of leakage current. The idea of La doping is known to restrain the formation of a non-ferroelectric second phase and to stabilize the perovskite phase. Also, as observed in Ref. 4, doping BiFeO3 films with L
Data Loading...
