Tailoring Magnetic Properties of Cubic Spinel Ferrite Core–Shell Nanoparticles for Magnetoresistive Engineering

Magnetite nanoparticles with a cobalt ferrite shell provide the opportunity to obtain a tunneling magnetoresistance structure and offer an additional degree of freedom in shaping the magnetoresistive characteristics. In order to investigate the effect of the relative fractions of the shell on magnetic and magnetoresistive properties, we have prepared (by chemical co-precipitation) a bi-magnetic (soft/hard) core–shell Fe3O4/CoFe2O4 nanoparticle system (with diameters of a few nm). The structural, magnetic, and electric transport properties of the as-prepared core precursor, core–shell nanoparticles, and sintered powder were determined. It was found that the obtained particles, which are few nanometers in size, have the desired single-crystalline spinel structure with a core–shell architecture and the expected magnetic properties associated with core–shell interactions. Sintering leads to more complex magnetic behavior and tunneling conductance.