Effects of stoichiometry on the magnetic and structural properties of perpendicular barium ferrite thin film media
The effects of stoichiometry factor n on the magnetic and structural properties of perpendicular barium ferrite thin films with composition of BaO.n(Fe/sub 2/O/sub 3/) were systematically investigated. Within the range 2.2<n<6, the c-axis for barium ferrite thin films can be oriented perpendicularly by the use of a Pt underlayer and with optimized processing conditions. Perpendicular c-axis orientation becomes worse as n decreases from 6 to 2.2. The average grain size was greatly reduced from about 2000 /spl Aring/ to 300 /spl Aring/ with the decrease of n. The decrease of the grain size can be related to the existence of nonmagnetic phase BaFe/sub 2/O/sub 4/, which was observed by X-ray diffraction.
Barium ferrite thin film media with perpendicular c-axis orientation and small grain size
Barium ferrite thin films with perpendicular c-axis orientation and small grain size (about 300 A) 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 (106) 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 p...
Crystallization phenomena in thin films of amorphous barium hexaferrite
Abstract It is an investigation on crystallization phenomena by post-deposition annealings of amorphous thin films of M type barium hexaferrite made either at room temperature (A samples) or at 400°C (B samples). Both amorphous layers were deposited by facing target sputtering system. The evolution of magnetic and crystalline properties of A and B samples were studied as a function of isochronous thermal treatments under air or oxygen. After different annealing steps, samples were characterized for the structure and the composition by X-ray and by secondary ion mass spectrometry respectively and for the magnetic properties by a vibrating sample magnetometer and by conversion electron Mossbauer spectroscopy. Stress measurements were also performed using a Fizeau interferometer. On the whole, it turns out that B samples are well textured, the c-axis being rather well perpendicular to the surface of the substance. This gives rise to the desired perpendicular anisotropy. As for A samples, they display isomorphous magnetic behaviour having no preferential crystalline orientation. Huge hydroxyl group absorption found in A with respect to B samples seems to be at the origin of discrepancies between the two amorphous hexaferrites made at different temperatures.