Electric-field control of the remanent-magnetic-state relaxation in a piezoelectric-ferromagnetic PZT-5%Fe₃O₄ composite

Magnetoelectric (ME) composites that exhibit both ferroelectric and ferromagnetic properties have attracted significant attention, thanks to their potential applications, e.g., low-energy-consumption storage devices. Here, we study bulk composites based on Pb(Zr_0.52Ti_0.48)O₃ (PZT) as a piezoelectric (PE) matrix and Fe₃O₄ nanoparticles (NPs) as soft ferromagnetic (FM) and magnetostrictive additives, in the form PZT-xFe₃O₄ with 0% ≤ x ≤ 50 wt. %, all sintered at T = 1000 °C for 2 h in air. We focus our study on a completely insulating sample x = 5% and measure its properties at room temperature upon an out-of-plane external electric field, E_ex: namely, piezoelectric response [in-plane strain, S(E_ex)], polarization [P(E_ex)], and relaxation of the remanent magnetization, [m_rem(t,E_ex)], prepared upon application and removal of an external magnetic field. The peaks observed in the butterflylike S(E_ex) curves at E^±_peak= ±6 kV/cm and the nucleation field recorded in the P(E_ex) loops at the same range around E^±_nuc= ±6 kV/cm (both referring to the PZT PE matrix) are clearly imprinted on the relaxation behavior of the m_rem(t,E_ex) data (referring to the Fe₃O₄ FM NPs). This experimental fact proves the ME coupling between the PZT matrix and the embedded Fe₃O₄ NPs. We ascribe this feature to the comparable piezoelectricity of the PZT matrix and the magnetostriction of the Fe₃O₄ NPs that probably motivate and/or promote a strain transfer mechanism occurring at the PZT matrix-Fe₃O₄ NP interfaces. Our work proves that the low cost PZT-xFe₃O₄ composite is a promising candidate ME material for future studies, aiming to potential applications. © 2019 Author(s).