Integration of Self‐Assembled Epitaxial BiFeO₃–CoFe₂O₄ Multiferroic Nanocomposites on Silicon Substrates

Abstract

Perovskite‐spinel epitaxial nanocomposite thin films are commonly grown on single crystal perovskite substrates, but integration onto a Si substrate can greatly increase their usefulness in devices. Epitaxial BiFeO 3 –CoFe 2 O 4 nanocomposites consisting of CoFe 2 O 4 pillars in a BiFeO 3 matrix are grown on (001) Si with two types of buffer layers: molecular beam epitaxy (MBE)‐grown SrTiO 3 ‐coated Si and pulsed‐laser‐deposited (PLD) Sr(Ti 0.65 Fe 0.35 )O 3 /CeO 2 /yttria‐stabilized ZrO 2 /Si. The nanocomposite grows with the same crystallographic orientation and morphology as that observed on single crystal SrTiO 3 when the buffered Si substrates are smooth, but roughness of the Sr(Ti 0.65 Fe 0.35 )O 3 promoted additional CoFe 2 O 4 pillar orientations with 45° rotation. The nanocomposites on MBE‐buffered Si show very high magnetic anisotropy resulting from magnetoelastic effects, whereas the hysteresis of nanocomposites on PLD‐buffered Si can be understood as a combination of the hysteresis of the Sr(Ti 0.65 Fe 0.35 )O 3 film and the CoFe 2 O 4 pillars.