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(Zr0.52Ti0.48)O-3 (PZT) as a piezoelectric (PE) matrix and Fe3O4 nanoparticles (NPs) as soft ferromagnetic (FM) and magnetostrictive additives, in the form PZT-xFe(3)O(4) with 0%<= x <= 50wt.%, all sintered at T=1000 degrees C for 2h 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(+/-)=+/- 6kV/cm and the nucleation field recorded in the P(E-ex) loops at the same range around E-nuc(+/-)=+/- 6kV/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-xFe(3)O(4) composite is a promising candidate ME material for future studies, aiming to potential applications.

Composite magnetoelectric compounds that combine ferroelectricity/piezoelectricity and ferromagnetism/magnetostriction are investigated intensively for room-temperature applications. Here, we studied bulk composites of a magnetostrictive constituent, ferromagnetic Fe3O4 nanoparticles, homogeneously embedded in a ferroelectric/piezoelectric matrix, Pb(Zr0.52Ti0.48) O-3 (PZT). Specifically, we focused on PZT-5%Fe3O4 samples which are strongly insulating and thus sustain a relatively high out-of-plane external electric field, E-ex,E-z. The in-plane strain-electric field curve (S(E-ex,E-z)) was carefully recorded upon successive application and removal of an out-of-plane external magnetic field, H-ex,H-z. The obtained S(E-ex,E-z) data exhibited two main features. First, the respective in-plane piezoelectric coefficients, d(E-ex,E-z) = 200-250 pm/V, show a dramatic decrease, 50-60%, upon application of a relatively low H-ex,H-z = 1 kOe. Second, the process is completely reversible since the initial value of d(E-ex,E-z) is recovered upon removal of H-ex,H-z. Polarization data, P(E-ex,E-z), evidenced that the Fe3O4 nanoparticles introduced static structural disorder that made PZT harder. Taken together, these results prove that the Fe3O4 nanoparticles, except for static structural disorder, introduce reconfigurable magnetic disorder that modifies the in-plane S(E-ex,E-z) curve and the accompanying d(E-ex,E-z) of PZT when an external magnetic field is applied at will. The room-temperature feasibility of these findings renders the PZT-x%Fe3O4 system a solid basis for the development of magnetic-field-controlled PE devices.