Enhancement of magnetization with decreased coercivity in nickel doped cobalt ferrite by coating with oleic acid

D. Vanidha¹ - A. Arunkumar¹ - S. Rajagopan² - R. Kannan¹

¹ Department of Physics, Pondicherry Engineering College, Puducherry-605014, India
² Department of Chemistry, Pondicherry Engineering College, Puducherry-605014, India

Abstract
Nanocrystalline Co _0.5Ni _xFe _0.5−xFe ₂O ₄ (x = 0.1 to 0.5) has been synthesized by a sol-gel citrate auto combustion method, keeping citric acid to the nitrate ratio as 3 : 1. XRD reveals the increased particle size and the absence of impurity peaks, confirming coating with oleic acid. Unique nature of coating in our system is found from enhanced saturation magnetization (M_S) due to the increase in number of carboxylic acid chains and decreased coercivity attributed to parallel spin nature between the FM core and the AFM shell with no loop shift. Confirmation of single layer coating with oleic acid is obtained from the absence of the peak at 1710 cm⁻¹ in FTIR studies. Variation in the resistance of the grain boundaries (R_gb) for coated and uncoated samples along with grain boundary contributed conductivity was observed. Tables 1, Figs 4, Refs 12.