| dc.description.abstract | High target utilisation sputtering (HiTUS) is a relatively new thin film deposition
technique that generates a high density plasma remotely from the sputter target.
This method has been employed firstly to investigate FePt and FePtN thin films
for high density data storage media applications and secondly to investigate the
production of a GMR/PZT hybrid structure (multi-ferroism) for improvements to
magneto-resistive read-sensor devices in hard disk drives and potentially for other
novel multi-ferroic applications.
The magnetic and structural properties of FePt and FePtN films, prepared by the
HiTUS method, on both silicon and glass substrates have been investigated before
and after annealing at temperatures in the range of 300 to 800 ◦C. It is shown that
during thermal annealing there is a degradation in magnetic properties of the FePt
films at around 400 ◦C due to the formation of silicides as the thermal processing
promotes the reaction of the film with the substrate. However, in the FePtN samples
coercivity values continue to rise with annealing temperatures above 400 ◦C. XRD
analysis confirms that silicide formation is suppressed in films containing nitrogen
up to 800 ◦C. Using the HiTUS technique, there is evidence that L10 ordering of
FePt has occured at annealing temperature of 400 ◦C with in plane and out of plane
coercivities of 7180 Oe and 6300 Oe respectively.
Finally, it is shown that HiTUS is capable of depositing ultra thin multilayer
GMR structures onto a variety of substrates; silicon, glass, flexible kapton film and
PZT. It is interesting to find that the GMR ratio obtained on kapton film (14.39
%) is almost as high as that on silicon (16.15 %), with much scope for improve-
ment. Multi-ferroic composite films consisting of the GMR multilayer structure
[Co(8 °A)/Cu(21 °A)]×20/Co(12 °A) on PZT substrates were fabricated and magneto-
electric coupling effects explored. It was found that AC voltages applied across the
composite GMR/PZT structure produced a marked decrease in the coercivity of the
GMR layer. However, DC voltages did not produce any measurable magnetic effects.
Careful investigation revealed that the reduction in coercivity observed during AC
measurements was, in fact, due to sample heating effects. | en_GB |
