Effect of Nd-Co substitution on magnetic and microwave absorption properties of SrFe12O19 hexaferrites

Nd-Co-substituted M-type strontium hexaferrites were prepared by sol-gel-autocombustion method. Crystalline structure, morphology, magnetic properties, and microwave absorption properties of Sr1-xNdxFe12-xCoxO19 (x = 0-0.4) were studied via X-ray diffraction, scanning electron microscope, vibrating sample magnetometer, and vector network analyzer, respectively. Single-phase M-type strontium hexaferrites, with a chemical composition of Sr1-xNdxFe12-xCoxO19 (x = 0-0.3), were formed by being heated at 1200 degrees C for 3 h in air. Saturation magnetization and coercivity reached a maximum at x = 0.2. For samples with x = 0.2, a minimum reflection loss of -22 dB was obtained at 16.2 GHz for a layer of 1.9 mm in thickness. The reflection loss of Sr0.8Nd0.2Fe11.8Co0.2O19 ferrite (1.5-3.0 mm in thickness) is less than -10 dB over the range of 9.8-18 GHz. It indicates that the substituted Nd-Co can greatly improve the microwave absorption properties of SrFe12O19 hexaferrites. (C) 2012 Elsevier B. V. All rights reserved.