Tailored magnetic properties in CoFeB–BiFeO3 nanocomposite thin films

Abstract

Ferromagnetic CoFeB (CFB) and multiferroic BiFeO₃ (BFO) are both extensively studied materials for thin-film device applications and have previously been implemented in multilayer or bilayer stacks. In this work, we demonstrate, for the first time, particle-in-matrix (PiM) films as a new CFB–BFO nanocomposite form. Two PiM films were deposited under nitrogen or vacuum atmosphere and compared against a more typical bilayer system. The different deposition conditions lead to microstructural tuning of the PiM films, with the two displaying inverted microstructures. The PiM films also displayed a large increase in the saturation magnetization compared to the bilayer film and slightly enhanced antiferromagnetic–ferromagnetic exchange coupling out-of-plane. All three films displayed ferroelectric properties, with the PiM film deposited under a nitrogen atmosphere showing significant leakage. These CFB–BFO nanocomposites present potential for future multiferroic device applications.