Perpendicular barium ferrite ͑BaM͒ films with Pt interlayers were successfully fabricated. The magnetic and structural properties of BaM films were compared with BaM films without Pt interlayers. It was found that perpendicular c-axis orientation was greatly improved for films with Pt interlayers. Perpendicular remanent squareness is increased, and the c-axis dispersion angle ⌬ 50 is decreased with Pt interlayers in BaM films. Also the coercivity was found to increase for films with Pt interlayers. A relative increase in perpendicular nucleation sites over in-plane and/or random nucleation sites contributes to the improvement in perpendicular c-axis orientation. The increase in coercivity may be explained by a weakening of magnetostatic interactions among BaM grains, due to magnetostatic isolation by the nonmagnetic Pt interlayers and the interdiffusion between Pt layers and BaM layers during high temperature ex situ annealing.

The effects of stoichiometry factor on the magnetic and structural properties of perpendicular barium ferrite thin films with composition of BaO (Fe 2 O 3) were systematically investigated. Within the range 2 2 6, the-axis for barium ferrite thin films can be oriented perpendicularly by the use of Pt underlayer and with optimized processing conditions. Perpendicular-axis orientation becomes worse as decreases from 6 to 2.2. The average grain size was greatly reduced from about 2000 Å to 300 Å with the decrease of. The decrease of the grain size can be related to the existence of nonmagnetic phase BaFe 2 O 4 , which was observed by X-ray diffraction.

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Barium ferrite thin films with perpendicular c-axis orientation and small grain size ͑about 300 Å͒ were successfully fabricated with careful control of sputtering conditions. The c-axis orientation of barium ferrite thin films is most sensitive to the oxygen partial pressure during deposition. All samples with oxygen gas during deposition have a random c-axis texture, as indicated by existence of both weak (00l) peaks and ͑106͒ peaks. All the samples without oxygen gas during deposition show only strong (00l) peaks, which indicate excellent perpendicular c-axis orientation. Transmission electron microscopy results show that oxygen gas promotes the growth of in-plane and/or randomly oriented grains. The effect of the Pt interlayer on the barium-rich films was also studied. The Pt interlayer was found to be very effective in improving c-axis orientation of barium-rich films. A relative increase in perpendicular nucleation sites over in-plane and/or random nucleation sites contributes to the improvement in perpendicular c-axis orientation.

Barium ferrite thin films with excellent perpendicular c-axis orientation were successfully fabricated on Si substrate without any buffer layer. To compensate for possible barium deficiency due to the inter-diffusion between films and substrate, a barium-rich target was used. For a 900 A-thick film, the perpendicular remanent squareness is about 0.9, while the in-plane remanent squareness is about 0.3. The saturation magnetization (Ms) is about 220 emu/cc, while the coercivity is around 3500 Oe. X-ray diffraction (XRD) results show the (001) perpendicular c-axis texture in the films. It was also found that the rapid thermal annealing conditions greatly affect the magnetic properties of barium ferrite films. With a certain flow rate of oxygen gas in the rapid thermal annealer (RTA), barium ferrite films generally crystallize with good perpendicular c-axis texture. Without oxygen gas, the hexagonal barium ferrite phase fails to develop; instead spinel Fe 3 0 4 phase forms. The reason for the collapsing of hexagonal barium ferrite texture is thought to be an oxygen deficiency in the barium ferrite films due to the reduction of oxygen in the films during the high temperature annealing.