In situ formation of composite thin film with (111) oriented Ni0.5Zn0.5Fe2O4 pillar array surrounded by BaTiO3 for ferroelectric-ferromagnetic coupling

Abstract

For a new breakthrough of highly efficient magnetoelectric (ME) coupling of multiferroic composite thin film in application of next generation multifunctional devices, it is important to control constituent magnetic phase pillar array independently embedded inside piezoelectric phase. In this work, in situ spin-coated xNi0.5Zn0.5Fe2O4/(1-x)BaTiO3 composite thin films on Si substrate with high magnetoelectric coupling are successfully obtained via phase separation. Results show that hexagonal Ni0.5Zn0.5Fe2O4 (NZFO) grain grows (111)-oriented as single crystal pillars arrayed independently uniformly and surrounded by BaTiO3 (BTO) phase. Ti and Fe ions are doped into the NZFO and BTO phases respectively and decreased with the decrease in corresponding constituent phases. Grain size and lattice constant of the cubic NZFO are from ~1 to ~0.5 μm and from 0.8383 nm to 0.8369 nm respectively in terms of x. The orientation degree of thin films is> 56% when x is above 0.8. The 0.8NZFO/0.2BTO thin film with and without pure BTO after-spincoated shows giant ME coupling effect, about 40% change of magnetization of NZFO in terms of phase transition of ferroelectric BTO at Curie temperature ~398 K. It is much larger than others on Si substrate ever reported and may be applied cost-effectively, coupling-efficiently and widely in Si-based chips area.