Abstract:

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.