The effect of Y3+ substitution on the structural, optical band-gap, and magnetic properties of cobalt ferrite nanoparticles. Issue 25 (19th June 2017) - Alves, T. E. P.
Abstract : In this study we investigated the structural, optical band-gap, and magnetic properties of CoY x Fe2− x O4 (0 ≤ x ≤ 0.04) nanoparticles (NPs) synthesized using a combustion reaction method without the need for subsequent heat treatment or the calcing process. Abstract : In this study we investigated the structural, optical band-gap, and magnetic properties of CoY x Fe2− x O4 (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 ( E g ) values increase with the Y 3+ 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, M s and remanent magnetization, M r, decrease from 69 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, H c, 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 H c 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 Y 3+ ion concentration and temperature. K 1 values for x = 0 ( x = 0.04) were 3.3 × 10 6 erg cm −3 (2.0 × 10 6 erg cm −3 ) and 0.4 × 10 6 erg cm −3 (0.3 × 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 Co 2+ ion distribution over tetrahedral A-sites and octahedral B-sites of the spinel structure due to Y 3+ ion substitution.