Inhibition of abnormal acicular grain growth of nanostructured Ba-ferrite films by secondary alpha-Fe2O3 phase

Abstract

We have studied the inhibition of abnormal acicular grain growth of the Ba-ferrite phase in the crystallization of Ba-ferrite films using real time synchrotron x-ray scattering, field emission scanning electron microscope, and vibrating sample magnetometer. Amorphous Ba-ferrite film on a SiO2 substrate is naturally crystallized into the abnormal acicular Ba-ferrite grains (major axis of similar to1000 nm in the in-plane direction). However, on alpha-Al2O3 substrate, fine grain sizes of the primary Ba-ferrite phase (similar to70 nm) are obtained during crystallization. Nucleation of the alpha-Fe2O3 phase on the alpha-Al2O3 surface at an early stage induces the inhibition of the abnormal acicular grain growth of the Ba-ferrite phase. Because of the grain size refinement of the magnetic Ba-ferrite phase, the intrinsic coercivity of Ba-ferrite/alpha-Al2O3 film enhances 4.4 kOe, much larger than that of Ba-ferrite/SiO2 film (1.9 kOe). We suggest that the secondary alpha-Fe2O3 phase act as a useful inhibitor to abnormal grain growth in Ba-ferrite films for high-density recording media. (C) 2002 American Institute of Physics.