Sol–gel hydrothermal synthesis of strontium hexaferrite nanoparticles and the relation between their crystal structure and high coercivity properties

Thi Minh Hue Dang, Viet Dung Trinh, Doan Huan Bui, Manh Huong Phan and Dang Chinh Huynh

Abstract

Hard magnetic strontium hexaferrite SrFe₁₂O₁₉ nanoparticles were synthesized by the sol–gel hydrothermal method. The factors affecting the synthesized process, such as the mole proportion of the reactants, pH, temperature, the hydrothermal conditions and the calcination process, have been investigated. The crystal structures of these materials were refined by Rietveld method. The obtained materials have single crystal phase, equal nano-size, plate shape and high anisotropy. The high magnetic coercivity of 6.3 kOe with the magnetization at 11.1 kOe of 66 emu g⁻¹ at room temperature was observed for the strontium hexaferrite nanoparticles. For other nanoparticles (SrLn_xFe_12-xO₁₉ and SrFe₁₂O₁₉/CoFe₂O₄) synthesized on the basis of SrFe₁₂O₁₉ the complex completion of the crystal structure distortion and the interaction between magnetic phases were observed