Magnetic stability against calcining of microwave-synthesized CoFe2O4 nanoparticles

Abstract

High quality CoFe₂O₄ nanoparticles were synthesized using a one-pot, microwave assisted method, that allows forming stable colloidal solutions in alcoholic solvents, as required for the preparation by Chemical Solution Deposition of hybrid nanocomposite ferromagnetic-high T_c YBa₂Cu₃O₇ superconducting films or devices. We have investigated how the thermal process necessary for the preparation of such epitaxial nanocomposites, involving high temperatures (800 °C) and oxygen partial pressures (1 atm), affects the structure and magnetic properties of the isolated nanoparticles. The NPs were fully characterised by XRD, SQUID, STEM-EELS and XMCD at four different stages of the thermal process. Results show that, despite intermediate changes in the cation distribution occur during the process, the final NP magnetization is stable against the thermal treatment. This result opens up perspectives for the preparation of hybrid YBCO films with embedded magnetic NPs using low-cost chemical-solution methods.