Local magnetoelectric effect in Fe3O4-BaTiO3 nanocomposites

Magnetoelectric nanoparticles (MENPs) are promising for biomedical applications. While cobalt ferrite-based MENPs exhibit strong magnetic properties, their biocompatibility remains uncertain. This study proposes iron oxide (FO) nanoparticles as a less toxic alternative and investigates the structural, crystalline, magnetic, and magnetoelectric (ME) properties of FO@BTO nanocomposites, where FO and barium titanate (BTO) provide magnetostrictive and piezoelectric functionalities, respectively. FO nanoparticles of three sizes (12.7, 25.9, and 47.7 nm) were synthesized and coated with BTO. Characterization using TEM, VSM, and XRD revealed that after annealing at 700 degrees C, BTO crystallite sizes increased from 8-9 nm to 11-13 nm. FO crystallite sizes remained stable for the 12.7 nm core sample but increased from 12.3 to 14.9 nm and from 12.8 to 17.0 nm for the 25.9 nm and 47.7 nm samples, respectively. VSM measurements show increasing coercivity and remanent magnetization with FO size: 12.7 nm cores exhibit superparamagnetic behavior (Hc = 0.1 Oe, Mr = 0.2 emu/g), while 47.7 nm cores show ferromagnetic behavior (Hc = 40.1 Oe, Mr = 10.9 emu/g). After BTO coating and annealing, magnetic characteristics decreased. The longitudinal magnetostriction coefficient was 6.5 ppm for 12.7 nm FO, 6.8 ppm for 25.9 nm, and 14.6 ppm for 47.7 nm. Piezoresponse force microscopy confirmed ME coupling, showing variations in the piezoelectric response under an applied magnetic field. These results highlight the potential of FO@BTO MENPs for magnetically controlled biomedical applications.