Comparison of surface effects in bare and titanium oxide coated CoFe2O4 nanoparticles

• Published in: Solid state sciences 2020-05, Vol.103, p.106186, Article 106186
• Main Authors: Zareef Khan, M., Nadeem, K., Zeb, F., Abbas, H., Ali, Basit, Letofsky-Papst, I.
• Format: Article
• Language: English
• Subjects: Cobalt ferrite; Magnetic properties; Surface effects; Titanium oxide
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2020.106186

Comparison of surface effects in bare and titanium oxide coated CoFe2O4 nanoparticles has been done with the help of magnetic measurements. The average crystallite size was 31 for bare CoFe2O4 nanoparticles. For titanium oxide coated nanoparticles, the CoFe2O4 and titanium oxide phases have crystallite size of 46 and 38 nm, respectively. TEM images confirmed the coating behavior of titanium oxide on CoFe2O4 nanoparticles. Both kinds of nanoparticles were in magnetically blocked state at room temperature as evident by ZFC/FC measurements. The effective anisotropy constant was calculated from simulated ZFC curve and found higher for bare CoFe2O4 nanoparticles due to large surface spin disorder and strong interparticle interactions. In modified Bloch's law fit for Ms vs. T data, the higher value of Bloch's constant for titanium oxide coated CoFe2O4 nanoparticles demonstrates the weak exchange coupling constant J. The Kneller's law fit for Hc vs. T data showed a lower value of constant α for titanium oxide coated CoFe2O4 nanoparticles which is due to the reduced surface magnetic and weak interparticle interactions. In summary, crystalline titanium oxide coating on CoFe2O4 nanoparticles showed reduction in surface spin disorder and weaken interparticle interactions. [Display omitted] •Surface effects get reduced in titanium oxide coated CoFe2O4 nanoparticles.•Particle size is not reduced in titanium oxide coated CoFe2O4 nanoparticles.•The titanium oxide coating has reduced the surface defects and interparticle interactions.