Fine Structure and Magnetic Properties of Ni – Zn Ferrite Nanoparticles Prepared by Ultrasonic Spray Pyrolysis

Abstract

Crystalline nano-sized Ni_1−xZn_xFe₂O₄ (x = 0～1.0) particles were prepared by ultrasonic spray pyrolysis from the spray sol-gel solution with Ni –, Zn – and Fe – nitrates and citric acid. The crystal lattice constant increased lineally with increasing Zn ion contents according to the Vegard’s rule. All the prepared particles had the size of less than 100 nm, which were calculated with Scherrer equation and were observed by TEM. The average particle size of the samples containing Zn ions was about 50 nm. The sample with x = 0.3 had the maximum magnetization of 63 emu/g, which was 80 percent of the bulk material. It was supposed that the sample contained a super paramagnetic substance. The coercivity of the samples was much larger than that of the bulk ferrites. The coercivity of the samples decreased with the increase of Zn ion contents. Curie temperature also decreased with the increase of Zn ion contents. However, these values were higher than those of the bulk materials because of existence of Fe²⁺ ions and heterogeneous octahedral site distribution of Zn ions.