Epitaxial multiferroic heterostructures

Epitaxial multiferroic composites have become a popular topic for the last few years, and several prototypes of devices based on these heterostructures have been proposed. In strain-mediated multiferroic systems, strong magnetoelectric coupling is expected between the order parameters of the ferroelectric and ferromagnetic components, because the lattice-matched interface is free of any foreign medium, which can transfer the mechanical coupling more efficiently than that in epoxy-bonded or polycrystalline bilayers. Charge- or exchange-bias-mediated magnetoelectric coupling that relies on uncompensated interfacial charges or spins can also be engineered at the nanoscale. In most of the studies on epitaxial multiferroic heterostructures, BiFeO3 (BFO), PZT, PMNPT, and PZNPT have been used as the ferroelectric layer, while the magnetic materials of choice include La-manganite ((La, Sr)MnO3), Ni/Co-ferrite (i.e., NiFe2O4, CoFe2O4), etc. In this chapter, we will give a brief review on the recent advances in the growth and characterization of these multiferroic heterostructures, and we will discuss future challenges and opportunities as well.