Hyperfine Interactions 156/157: 97–102, 2004. © 2004 Kluwer Academic Publishers. Printed in the Netherlands. 97 Synthesis of Nanocrystalline Ni 0.5 Zn 0.5 Fe 2 O 4 by Aerosol Route and Its Characterization SONAL SINGHAL 1 , A. N. GARG 2 and KAILASH CHANDRA 1,∗ 1 Institute Instrumentation Centre, Indian Institute of Technology-Roorkee, Roorkee 247 667, India; e-mail: chandfuc@iitr.ernet.in 2 Department of Chemistry, Indian Institute of Technology-Roorkee, Roorkee 247 667, India Abstract. Nano-size particles of Ni 0.5 Zn 0.5 Fe 2 O 4 ferrite were prepared through aerosol route. The solutions of iron, nickel and zinc nitrates were mixed in stoichiometric proportion, passed through a pneumatic nebulizer, to get very fine mist (aerosols), and a furnace at ∼600 ◦ C in air atmosphere. Through various events in succession, metal atoms form ferrite in air. The average particle size was found to be 16±6 nm which increased to 80±8 nm after annealing at 1000 ◦ C. The room-temperature magnetic moment of the sample as obtained and after annealing it at various temperatures indicate that the saturation magnetization increases from 1.80 to 72.8 emu/g, while remanent magnetization increases from 0.28 to 25.0 emu/g. Mössbauer spectrum of the sample at room temperature exhibited a doublet with δ(Fe) = 0.33 mm s −1 and E Q = 0.78 mm s −1 suggesting superparamagnetic nature. However, after annealing at 1000 ◦ C this doublet got converted into two magnetic sextets with B = 52.4 T and 49.0 T suggesting increase in particle size on annealing. These observations are in conformity with Transmission Electron Microscope (TEM) and X-Ray Diffraction (XRD) results that the particle size increases after annealing the sample at higher temperatures. 1. Introduction Since the last decade interesting magnetic properties have been reported for nano- crystalline spinel ferrites [1–3]. A reduction in particle size to the nanometer scale results in various special properties such as the quantum-size effects, the high sur- face area and the lower sintering temperature which is base to obtain fine grain size ceramics with advanced properties, etc. [1, 2]. Ni–Zn ferrites with the spinel crystal structures have been extensively used in many electronic devices because of their high permeability at high frequency, remarkably high electrical resistiv- ity, mechanical hardness, chemical stability and reasonable cost [4]. The electri- cal and magnetic properties of Ni–Zn ferrites depend strongly on oxidation state and distribution of cations of the tetrahedral (A) and octahedral (B) sites in the lattice [5, 6]. Sedlar et al. [7] synthesized nickel zinc ferrite (Ni 0.36 Zn 0.64 Fe 2 O 4 ) thick films using a dip coating sol–gel process and suggested that the suitable processing temperature is 400 ◦ C for the preparation of films with reasonable magnetic prop- * Author for correspondence.