Cl-2/He, Cl-2/Ar, and Cl-2/Xe discharges operated under inductively coupled plasma conditions have been compared for patterning of Ni0.8Fe0.2 and Ni0.8Fe0.13Co0.07 layers. There is a transition from net deposition to etching with increasing source power, as the relatively involatile chlorinated etch products are removed more efficiently by ion-assisted desorption. This transition occurs at lower ion fluxes for Xe-and Ar-containing discharges than for He due to the more effective momentum transfer. The etch rates with all three mixtures also go through maxima, reflecting the need to balance etch product formation and desorption.