Embodiments disclosed herein generally relate to a TMR sensor for reading a recording from a magnetic recording medium using TMR, and in particular, to a magnetic capping structure of the TMR sensor. The sensor comprises a free layer and a magnetic capping structure. The magnetic capping structure comprises a ferromagnetic capping layer and an absorption layer formed on the ferromagnetic capping layer. The absorption layer is adapted to absorb molecules from the ferromagnetic capping layer and prevent the ferromagnetic capping layer from diffusing into the free layer.