Tailored Magnetic Properties in CoFeB-BiFeO3 Nanocomposite Thin Films

Abstract

Ferromagnetic CoFeB (CFB) and multiferroic BiFeO3 (BFO) are both widely studied materials for thin film device applications and are previously 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 and vacuum atmospheres and compared against a more typical bilayer system. The different deposition conditions lead to microstructure 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.