A comparison of the magnetism of cobalt-, manganese-, and nickel-ferrite nanoparticles

Abstract

The microstructure, composition and magnetism of CoFe2O4, MnFe2O4 and NiFe2O4 nanoparticles of comparable sizes (similar to 20 nm) and interparticle spacings (similar to 20 nm) have been characterized from 10 to 400 K. The cation distributions of the tetrahedral and octahedral sites of the particles, that have cubic spinel structures, have a high degree of inversion, similar to 0.98 for CoFe2O4, similar to 0.80 for MnFe2O4 and NiFe2O4 nanoparticles. The blocking temperatures were similar to 300 K for the MnFe2O4 and NiFe2O4 nanoparticles, while the CoFe2O4 nanoparticles, due to their higher intrinsic anisotropy had a significantly higher blocking temperature above 400 K. Specifically, the magnetocrystalline anisotropy of the CoFe2O4 nanoparticles was K = ( 2.96 +/- 0.03) x 10(6) ergs cm(-3), while for the MnFe2O4 nanoparticles, K = ( 0.04 +/- 0.01) x 10(6) ergs cm(-3), and for the NiFe2O4 nanoparticles, K = ( 0.07 +/- 0.01) x 10(6) ergs cm(-3). The magnetism of these three ferrite systems are discussed in detail with regards to their microstructures and cation distributions.