Vol.:(0123456789) 1 3 Appl. Phys. A (2017) 123:685 DOI 10.1007/s00339-017-1323-5 Ferroelectrically induced dual band microwave absorption in multiferroic BiFeO 3 /acrylo-nitrile butadiene rubber composites Lokesh Saini 1,2  · Sunil Kumar Barala 2  · Manoj Kumar Patra 1  · Raj Kumar Jani 1  · Ambesh Dixit 2  · Sampat Raj Vadera 1   Received: 25 June 2017 / Accepted: 12 October 2017 © Springer-Verlag GmbH Germany 2017 black [5]/nanotubes (CNT’s) [6], graphene [7], carbonyl iron [8], ferrites [9, 10], etc., are being explored by researchers to counter these measures. There is continuous thrust for exploring new materials with their structure—property-pro- cess dependent functional properties in this area to overcome such challenges. Multiferroics are a class of materials wherein electric, magnetic, and structural order parameters are coupled, resulting in simultaneous onset of ferroelectricity, magnet- ism, and ferroelasticity in the single phase material [11]. The multiferroic systems ofer advantages over conventional magnetic and ferroelectric materials due to their magneto- electric coupling between ferroelectric and magnetic order- ing in the single phase material. These materials exhibit contradictory physical characteristics of both magnetic and ferroelectric ordering in single phase material (where mag- netic ordering requires unflled d/f orbitals and ferroelectric ordering demands d 0 or completely flled d orbitals) [12, 13]. The presence of more than one ferroic ordering may provide enhanced absorption of MW energy over extended frequency window for several applications. The BiFeO 3 (BFO) perovskite oxide system has been extensively stud- ied for its structural, electrical, magnetic and multiferroic properties due to the simultaneous presence of ferroelectric- ity with high Curie temperature (T c ~ 1100 K) and G-type antiferromagnetic ordering with high Neel temperature (T N ~ 640K) [14–16]. At room temperature, BFO is a dis- torted rhombohedral crystal system with lattice parameters (a = b = c) rh = 3.965 A° and α = 89.3–89.48 °C and arranged in R3c space group symmetry [17]. The Bi 3+ cations are placed at eightfold coordinated corner sites of a cubical unit and Fe 3+ at the center of cubical structure within the cage of oxygen octahedron. The two cubic BFO unit cells are settled along [111] direction with a relative displacement of cations with respect to O 2− anions in R3c space group Abstract Nanostructured multiferroic BiFeO 3 powder has been synthesized using sol–gel route followed by optimized post-annealing treatment. The phase pure rhombohedral structure of prepared powder was confrmed by X-ray dif- fraction and Fourier transform infrared studies. The room temperature weak ferromagnetic nature (~ 0.15 emu/g) exhibited by the nanocrystalline BiFeO 3 sample (~ 50 nm) is attributed to the canted spin ordering in the sample. The BiFeO 3 /NBR rubber composites, with 50–80 wt% fller loading fractions, show the dual band resonating micro- wave (MW) absorption behavior. The refection loss (R.L.) values enhanced and required absorber thickness reduced simultaneously with increasing BiFeO 3 loading fraction in composite samples. These results confrm that the ferro- electric properties of multiferroic BiFeO 3 are contributing signifcantly for the observed MW absorption with respect to the magnetic contribution. 1 Introduction The modern technology poses several threats for micro- wave radiation in civil as well as defence sectors, e.g., unhealthy EM pollution, EMI interferences, detection of strategic aerial vehicles by enemy’s radar [1–3], etc. The conventional microwave absorbing materials of dielectric and magnetic class, viz. conducting polymer [4], carbon * Ambesh Dixit ambesh@iitj.ac.in 1 Materials Development Group, Defence Laboratory, Ratanada Palace, Jodhpur 342011, India 2 Department of Physics and Center for Solar Energy, Indian Institute of Technology Jodhpur, Jodhpur 342011, India