Magnetic Properties of Iron Implanted Polymers and Graphite

Abstract

ABSTRACTWe have measured the magnetic properties of highly oriented pyrolytic graphite (HOPG), polyethylene (PE), and polyvinylidine fluoride (PVF2), implanted with fluences of 25 keV iron atoms ranging from 1016 to 1017 atoms/cm2 . The lowest fluence specimens were paramagnetic down to 2 K, with evidence for clusters of only a few spins, while the highest fluence specimens were clearly ferromagnetic, with magnetization curves resembling those of a set of randomly oriented soft magnetic planes. The critical fluence for formation of a ferromagnetic state appears to be between 1 and 3 × 1016 atoms/cm2 at 25 keV. Theseresults can be qualitatively understood based on the critical density for percolation of near neighbor exchange interactions.