Non-monotonic Coercivity of Iron Filled Carbon Nanotube/Polystyrene Composites

Ravi Bhatia and I. Sameera


Multiwall carbon nanotubes (MWCNT) filled with magnetic nanoparticles constitute a fabulous magnetic system due to the fact that encapsulated magnetic nanoparticles remain protected from both aggregation and oxidation. Such a magnetic system has exotic properties, e.g. an enhanced magnetic coercivity. The coercivity is observed to get further enhanced if these magnetic nanoparticles filled MWCNT are homogeneously dispersed into a polymer matrix. We attempted to investigate the magnetic response of iron filled-multiwall carbon nanotubes (Fe-MWCNT) by dispersing them in polystyrene (PS) in different amounts. In this fashion we prepared Fe-MWCNT/PS composites of 0.1 to 7.0 wt%, and studied the variation in coercivity (Hc) of composites at 300, 150 and 10 K. An unexpected non-monotonic variation in the value of Hc of Fe-MWCNT/PS composites as function of Fe-MWCNT loading is understood qualitatively by considering the effect of inter-particle separations on dominant magnetic interactions.

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