Crystal structures and magnetic properties of silica and polyethylene glycol (PEG-4000) — Encapsulated Zn<inf>0.5</inf>Ni<inf>0.5</inf>Fe<inf>2</inf>O<inf>4</inf> magnetic nanoparticles

Abstract

Nanocrystalline mixed spinel ferrite of Zn 0.5 Ni 0.5 Fe 2 O 4 nanoparticles has been successfully synthesized by coprecipitation method and encapsulated by silica and PEG-4000 with various concentrations. X-Ray Diffraction (XRD) patterns showed that nanoparticles contained Zn 0.5 Ni 0.5 Fe 2 O 4 spinel ferrite with crystallite size of 15.2 nm. After silica encapsulation the new phase of SiO 2 appearance and the crystallite size became 14.1 nm. After PEG-4000 encapsulation also appeared a new phase of a-Fe 2 O 3 and the crystallite size became 13.3 nm. Transmission Electron Microscopy (TEM) image showed that the nanoparticles more dispersed and decrease agglomeration after silica and PEG-4000 encapsulation. The coercivity (H c ) of Zn 0.5 Ni 0.5 Fe 2 O 4 was 50.7 Oe. The H c decrease after silica and PEG-4000 encapsulation became 45,2 Oe and 47.9 Oe, respectively. It is due to the decrease of particle size. The saturation magnetization (M s ) of Zn 05 Ni 0 . 5 Fe 2 O 4 was 18.4 emu/g, and decrease to 16.8 emu/g after silica encapsulation because SiO 2 is non-magnetic properties. M s decrease to 17.1 emu/g after PEG-4000 encapsulation. This is because PEG-4000 has paramagnetic properties. Fourier Transform Infra Red (FTIR) spectra for Zn 05 Ni 05 Fe 2 O 4 show that the absorbtion peaks is around 300–600 cm−1 which is an M-O bond vibration. After a silica encapsulation, there are new bond vibration typical of silica like Si-O-Si (1087.85 cm−1), Si-OH (794.67 cm−1), and Si-O-Fe (574.64 cm−1). The PEG-4000 encapsulation has new vibration for typical of PEG like C-O (1064.71 cm−1). Both of encapsulation has M-O bond vibration indicates the presence of Zn 0.5 Ni 0.5 Fe 2 O 4 nanoparticles.