Investigation of size dependent Curie temperature and magnetization of bismuth substituted zinc ferrite (ZnBi_xFe_2−xO₄) nanoparticles

Abstract

The spinel zinc-bismuth ferrites with nominal composition of ZnBi_xFe_2−xO₄ (x = 0, 0.5, 0.1, 0.15, 0.2, 0.25, 0.3) have been synthesized by ball milling technique. Commercially available bismuth, zinc and iron oxide powders were first mixed and then annealed at 1100 ^°C in an oxygen environment furnace for 10 h. The samples were then milled for 2 h in a Fritsch mille. The average grain size were estimated from the X-ray line broadening of the (311) reflection and transmission electron microscopy (TEM). The micro and nanostructure investigation was carried out by a scanning electron microscope (SEM) with maximum magnification of 20,000. Magnetic properties of the as-prepared ferrites were studied by means of alternating gradient force magneto-meter (AGFM) and Faraday balance measurement. An increasing bismuth content in ZnBi_xFe_2−xO₄ leads to a decrease in the saturation magnetization, coercive field and Neel temperature. These results can be attributed to the substitution of Bi³⁺ ions in the ferrite system as nonmagnetic cations.