Oxygen Incorporation into Electrodeposited CoFe Films: Consequences for Structure and Magnetic Properties

The nanostructure and magnetic properties of electrodeposited Co40Fe60 alloy films containing varying amounts of oxygen were investigated using transmission electron microscopy (TEM) and diffraction, secondary ion mass spectroscopy (SIMS), and superconducting quantum interference device (SQUID) measurements. Oxygen content in the CoFe deposit was controlled by electrolyte composition. Films were deposited on Si {100} substrates with thin Cu/Ti seed layer. Electron energy loss and x-ray spectroscopies showed that the low oxygen films contained intragranular FeO particles and that the high oxygen films contained Fe2O3 along grain boundaries. The films with oxide present at the grain boundary had increased coercivity and reduced saturation magnetization relative to the lower oxygen content films with intragranular oxide. The differences in magnetic properties between low oxygen and high oxygen concentration films were attributed to stronger mobile domain wall interactions with the grain boundary oxide layers relative to interactions with the intragranular oxide particles in the low oxygen specimens.