Abstract
We report the influence of Co concentration on the exchange bias and magnetocrystalline anisotropy of CoxFe3-xO4 (x = 0.0, 0.4, 0.7, 1.0) nanoparticles. Co ions were substituted in magnetite (Fe3O4) nanoparticles to obtain non-stoichiometric CoxFe3-xO4 nanoparticles. The concentration of Co (mol) was varied from 0.0 to 1.0. Structure and magnetic anisotropic properties of non-stoichiometric CoxFe3-xO4 nanoparticles were studied. The prepared CoxFe3-xO4 nanoparticle was quasi-spherical in shape with particle sizes ranging from 15 to 20 nm. Raman and X-ray photoelectron spectroscopic (XPS) studies suggest the transformation of inverse to normal spinel structure concerning Co concentration. Blocking temperature increases from 155 to 302 K with an increase in concentration (mol) from 0.0 to 1.0 respectively. CoxFe3-xO4 (x = 0.7) resulted in an exchange bias field and large magnetocrystalline anisotropy of about 70 Oe and 5.38 x 10(4) J/m(3). Due to large magnetocrystalline anisotropy, CoxFe3-xO4 (x = 0.7) shows a low exchange bias field. CoxFe3-xO4 (x = 1.0) show room temperature hysteresis with coercivity of about 14.5 kOe at 5 K and M-S of 45 emu/g.