Physical and Magnetic Characterization of Hard/Soft SrFe12O19/CoFe2O4 Nanocomposite Magnets Made by Mechanical Alloying and Ultrasonic Irradiation

Abstract

In this study, the particle sizes of SrFe₁₂O₁₉ in hard/soft SrFe₁₂O₁₉/CoFe₂O₄ nanocomposite magnets made using mechanical alloying and ultrasonic irradiation were investigated. SrFe₁₂O₁₉/CoFe₂O₄ nanocomposites were combined in a ratio of 75:25, with each magnetic material being prepared separately. SrFe₁₂O₁₉ powder was prepared from Fe₂O₃ and SrCO₃ powder by mechanical alloying and ultrasonic irradiation for different times, 0, 3, 6, 9, and 12 h. Varying the ultrasonic time during the preparation of the SrFe₁₂O₁₉ samples resulted in differences in morphological characteristics, crystal structure, particle size, crystal size, microstrain, density, porosity, and magnetic properties. The longer the ultrasonic time, the crystal size and particle size decreases, the density increases, and the porosity reduction which affects the magnetic properties. SrFe₁₂O₁₉ after 12 h ultrasonic process reach M_s value = 61.29 emu/g. CoFe₂O₄ powder was produced from Fe₂O₃ and CoCO₃ powder by mechanical alloying with a 10 h milling time. Furthermore, each SrFe₁₂O₁₉ sample was composited with CoFe₂O₄ powder by ultrasonic irradiation for 1 h and these composite samples also showed different characteristics, where there is an increase in M_r and M_s compared to the single SrFe₁₂O₁₉. The morphology, crystal structure, particle size, and magnetic properties of the samples were measured using scanning electron microscopy, X-ray diffraction, particle size analysis, and PERMAGRAPH. The crystal size and microstrain were calculated using a Williamson–Hall plot, and density and porosity were determined using Archimedes’ law.