Direct Synthesis of L 1 0 -Phase Nanostructured CoPt Thin Films Using Dense Plasma Focus Device Operating in Non-optimiz
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1250-G08-04
Direct Synthesis of L10-Phase Nanostructured CoPt Thin Films Using Dense Plasma Focus Device Operating in Non-optimized Focus Mode
Zhenying Pan1, Rajdeep S. Rawat1, Jiaji Lin2, Shumaila Karamat1, Paul C.K. Lee1, Stuat V. Springham1, Augustine T.L. Tan1, 1
NSSE, National Institute of Education, Nanyang Technological University, 1 Nanyang walk,
Singapore 637616 2
Solar Energy Research Institute of Singapore, National University of Singapore, 7 Engineering
Drive 1, Singapore 117574
ABSTRACT A direct synthesis of (001) oriented nanostructured CoPt thin films has been successfully achieved using a 880 J pulsed Dense Plasma Focus (DPF) device operating in a non-optimized focus mode with a low charging voltage of about 8 kV. The (001) oriented fct structured L10 phase nanostructured CoPt thin films have been synthesized directly in as-deposited sample, as verified by XRD results, without any post deposition annealing. The SEM imaging results show that nanostructured CoPt were achieved in non-optimized focus mode with agglomerate/particle size ranging from 10 to 55 nm. Furthermore, the VSM analysis shows that the as-deposited samples in non-optimized focus mode have higher coercivity (due to direct L10 phase) as compared the annealed sample and the as-deposited sample of optimized focus mode operation. INTRODUCTION The CoPt binary alloy is an excellent system because it has both chemical stability and high magnetocrystalline anisotropy which has received significant attention as possible high density magnetic recording media owing mainly to the existence of ordered intermetallic phases with exceptionally hard magnetic properties. The ordered fct structure L10 CoPt nanoparticles have a large magnetic anisotropy of about 4.9×107erg/cc [1], hence the thermal agitation would be suppressed due to their large magnetic energy, which makes it a potentially interesting material from a commercial standpoint. From the practical application points of view, the magnetic data storage requires: (i) small particle size with tight size distribution; (ii) fct phase with high magnetocrystalline anisotropy and preferred (001) oriented crystal to overcome the superparamagnetism; and (iii) well-separated nanoparticles for reduced exchange coupling effects. Hence these are three key challenges for practical data storage applications of L10 phase CoPt nanoparticles nowadays. CoPt nanoparticles have been produced using various techniques, such as chemical methods [2,3] and physical thin film deposition techniques including pulsed laser deposition (PLD) [4], the radio-frequency (RF) sputtering [5], molecular beam epitaxy (MBE) [6], etc. In our research work, we used a Dense Plasma Focus (DPF) device as a pulsed plasma deposition source for nanostructured L10-CoPt thin films synthesis. Being a source of a wide range of phenomena,
DPF has found applications in material science. Many different kinds of thin films have been deposited and processed using DPF [7-11]. It has been reported that the energetic ions of the DPF device can b
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