Microstructure and Properties of Well-Ordered Multiferroic Pb(Zr,Ti)O3/CoFe2O4 Nanocomposites

A nanofabrication technique combining pulsed laser deposition and a nanoporous anodic aluminum oxide membrane mask is being proposed to prepare various types of multiferroic nanocomposites, viz. periodically ordered CoFe2O4 dots covered by a continuous Pb(Zr,Ti)O-3 layer, Pb(Zr,Ti)O-3 dots covered with CoFe2O4, and Pb(Zr,Ti)O-3/CoFe2O4 bilayer heterostructure dots. By properly tuning the processing parameters, epitaxial nanodot-matrix composites can be obtained. For the composite consisting of CoFe2O4 nanostructures covered by a Pb(Zr,Ti)O-3 film, an unexpected out-of-plane magnetic easy axis induced by the top Pb(Zr,Ti)O-3 layer and a uniform microdomain structure can be observed. The nanocomposites tested by piezoresponse force microscopy (PFM) exhibit strong piezoelectric signals, and they also display magnetoelectric coupling revealed by magnetic-field dependent capacitance measurement.