Cap layer able to be reactive ion etched for RSB DFL read elements

A dual free layer (DFL) read head, comprising:

• a tunnel magneto resistance (TMR) sensor disposed at a media facing surface (MFS);
• soft bias (SB) side shields disposed adjacent to the TMR sensor at the MFS;
• and
• a rear soft bias (RSB) disposed adjacent to the TMR sensor recessed from the MFS, the RSB having a nonmagnetic cap, the nonmagnetic cap comprising:
• a first nonmagnetic cap layer;
• and
• a second nonmagnetic cap layer, the second nonmagnetic cap layer being disposed on the first nonmagnetic cap layer, wherein an etch selectivity of the first nonmagnetic cap layer to the second nonmagnetic cap layer is a ratio of a:b in a first chemistry and a ratio of x:y in a second chemistry, wherein a is greater than b, and y is greater than x, wherein the first nonmagnetic cap layer comprises carbon and the second nonmagnetic cap layer comprises silicon, or wherein the first nonmagnetic cap layer comprises tantalum and the second nonmagnetic cap layer comprises ruthenium.