Magnetic and microwave absorption property of SrAl₄Fe₈O₁₉ powders synthesised via co-precipitation method
by H.Y. He, Z. He, Qing Shen
International Journal of Nanomanufacturing (IJNM), Vol. 7, No. 1, 2011

Abstract: Al-substituted M-type hexaferrite is a high anisotropy material. In this paper, we report the co-precipitation synthesis of SrAl₄Fe₈O₁₉ powder and their anisotropy, and magnetic and microwave absorption property. The experiment results indicated that the SrAl₄Fe₈O₁₉ powder required a calcining time of 3 h to forming pure hexagonal platelike SrFe₁₂O₁₉. The shape anisotropy of the powders decreased with the preheating. The coercivity decreased but magnetisation increased as decrease in shape anisotropy, but had no concern with the c/a value. The specimen without preheating had a maximum coercivity of 3.9947 kG and minimum magnetisation of 13.471 A·m²·kg⁻¹. However, the specimen preheated at 400°C had a minimum coercivity of 2.9503 kG and maximum magnetisation of 32.266 A·m²·kg⁻¹. The reflection losses were more than -20 dB in range of 7 GHz nearby strongest resonance frequencies of -14.7 GHz and -19.5 GHz for specimen with no preheating and preheating of 300°C, and in range of 5 GHz nearby strongest resonance frequencies of -14.2 GHz and -18.5 GHz for the specimens with preheating of 400°C. Al-substitution obviously increased anisotropy of the Sr-hexaferrite, and so increased ferromagnetic resonance frequency. Small particle size resulted from preheating might be effective for increasing reflection loss.

Online publication date: Sat, 28-Feb-2015

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