Crystal structures and magnetic properties of silica-encapsulated COZnFe 2 O 4 magnetic nanoparticles

Zinc-doped cobalt ferrite magnetic nanoparticles (CoZnFe <inf>2</inf> O <inf>4</inf> ) with silica encapsulation have been successfully synthesized by using coprecipitation method. The concentration of silica was varied by 0 , 5 , 10 , 15 , 20 , 30 and 50 of weight. The XRD spectra show that all samples have the character of the main spinel diffraction peaks (2θ) attributed to the (220), (311), (400), (422), and (511) planes. The FTIR analysis shows that the intrinsic stretching vibrations of metal-oxygen at the frequency range of 393 cm ¹ -401 cm ¹ and 470 cm ¹ -563 cm ¹ were found at octahedral and tetrahedral sublattices, respectively. The unencapsulated CoZnFe <inf>2</inf> O <inf>4</inf> nanoparticle has coercivity (Hc) and maximum magnetization (M) of 251 Oe and 29.0 emu/gram, respectively. The coercivity value of the encapsulated nanoparticles increases up to 853 Oe with the increase of silica concentration, while the maximum magnetization decreases to 24.2 emu/gram. © The Korean Magnetics Society. All rights reserved.