Arc discharge is one of the most efficient approaches to fabricate graphite-encapsulated magnetic nanoparticles. However, given the ultra-fast synthetic procedure, the understanding of tailoring shell morphology and quality over magnetic core has been a long standing challenge. To better comprehend the mechanism of the encapsulating shell growth in plasma, a series of synthetic parameters were investigated systematically in this study. Specifically, (1) the surface morphology of the outmost shell evolved with high integrity by adding CH4 concentration from 0% to 50% to He background gas; (2) a smooth surface with higher graphitization degree was achieved by changing collecting zone closer to the arc center; (3) carbon nano loops on the outmost shell expanded volumetrically to be continuous amorphous cover as the working gas pressure decreases from 100 to 25 Torr. The surface properties (i.e., zeta potential and acid-base character) were also evaluated and explained through XPS technique. (C) 2017 Elsevier B.V. All rights reserved.