Study of Magnetic Interactions in a Composite with a Mixture of γ-Fe2O3 and CoFe2O4 Nanoparticles

Magnetic interactions in composites promising for biomedical applications were studied. The composites were based on a piezoactive PVDF matrix filled with various systems of particles: hard magnetic CoFe2O4 nanoparticles, a mixture of soft magnetic γ-Fe2O3 and hard magnetic CoFe2O4 nanoparticles, and a mixture of CoFe2O4 and BaTiO3 particles. The study was made by the IRM–DCD and FORC methods. It was determined that the presence of a soft magnetic phase in the composite leads to an increase in the magnetic interaction fields from ∼1300 Oe (for composites containing CoFe2O4 particles) to ∼1500 Oe (for composites containing a mixture of hard and soft magnetic nanoparticles) and to the formation of two main magnetic phases in the composite.