The role of Ga substitution on magnetic and electromagnetic properties of nano-sized W-type hexagonal ferrites

A series of nano-sized single phase W-type SrGaxZn2Fe16-xO27 (x = 0.0, 0.1, 0.2, 0.3, 0.4) hexaferrites prepared by sol gel technique and sintered at 950 degrees C have been investigated. The thermal decomposition behavior of nitrate-citrate gel of as prepared powder was investigated by means of DTA/TGA analysis. The sintered powders were characterized by FTIR, XRD, SEM, VSM and vector network analyzer (VNA). X-ray diffraction patterns for pure and substituted W-type hexaferrites show the single phase structure with no impurity phase. The lattice parameters (a and c) decrease with the increase of Ga contents (x). The grain size estimated from SEM images is in the range of 139-76 nm which confirms the nanocrystalline nature of the investigated samples. The saturation magnetization (M-S) decreases whereas coercivity (H-C) increases with the increase of Ga contents (x). The values of H-C for all of the investigated samples lie in the range of few hundred oersteds which is one of the necessary conditions for EM materials. The microwave absorption property is enhanced in the frequency (with respect to -20 dB) from 0.5 to 13 GHz, and the bandwidth reaches 0.899 GHz. The attenuation peak value is 32 dB at the matching thickness of 3.4 mm. (C) 2012 Elsevier B.V. All rights reserved.