The effect of Y3+ substitution on the structural, optical band-gap, and magnetic properties of cobalt ferrite nanoparticles

In this study we investigated the structural, optical band-gap, and magnetic properties of CoYxFe(2-x)O(4) (0 <= x <= 0.04) nanoparticles (NPs) synthesized using a combustion reaction method without the need for subsequent heat treatment or the calcing process. The particle size measured from X-ray diffraction (XRD) patterns and transmission electron microscope (TEM) images confirms the nanostructural character in the range of 16-36 nm. The optical band-gap (Eg) values increase with the Y3+ ion (x) concentration being 3.30 and 3.58 eV for x = 0 and x = 0.04, respectively. The presence of yttrium in the cobalt ferrite (Y-doped cobalt ferrite) structure affects the magnetic properties. For instance, the saturation magnetization, Ms and remanent magnetization, M-r, decrease from69 emu g(-1) to 33 and 28 to 12 emu g(-1) for x = 0 and x = 0.04, respectively. On the other hand the coercivity, Hc, increases from 1100 to 1900 Oe for x = 0 and x = 0.04 at room temperature. Also we found that M-s, M-r, and Hc decreased with increasing temperature up to 773 K. The cubic magnetocrystalline constant, K-1, determined by using the "law of approach'' (LA) to saturation decreases with Y3+ ion concentration and temperature. K-1 values for x = 0 (x = 0.04) were 3.3 x 10(6) erg cm(-3) (2.0 x 10(6) erg cm(-3)) and 0.4 x10(6) erg cm(-3) (0.3 x 10(6) erg cm(-3)) at 300 K and 773 K, respectively. The results were discussed in terms of inter-particle interactions induced by thermal fluctuations, and Co2+ ion distribution over tetrahedral A-sites and octahedral B-sites of the spinel structure due to Y3+ ion substitution.