Hexaferrite/α-iron composite nanowires: Microstructure, exchange-coupling interaction and microwave absorption

The magnetic hexaferrite SrFe12O19 (SFO, magnetic hard phase)/alpha-Fe (F, magnetic soft phase) composite nanowires (SFCNWs) with diameters about 100 nm and high aspect ratios have been synthesized by the organic gel-thermal selective reduction process. The SFO and F nanocomposites are formed after the selective reduction of the oxide precursor at 375 degrees C for 1 h. The magnetic property difference of these SFCNWs measured at 297 K and 77 K largely arises from the competition of magnetic exchange-coupling interaction and thermal fluctuation on dipolar interactions. With the mass ratios (SFO/F) increase, the minimum reflection loss (RL) with 3.0 mm thickness reaches the optimized value of -51.1 dB at 10.4 GHz for the mass ratio (SFO:F) of 7:3. While the microwave absorption bandwidth exceeding -20 dB with a thickness of 4.0 mm covers the whole G-band, X-band and 20% Ku-band. The comparison of microwave absorption for the nano-and micro-wires of SFO and F nanocomposites is also investigated. (C) 2014 Elsevier B.V. All rights reserved.