A magnetic sensor is configured to reside in proximity to a recording medium during use. The sensor includes a magnetic top shield and a magnetic bottom shield. A top sensor stack is under the magnetic top shield and includes magnetic sensing layers. A bottom sensor stack is between the magnetic bottom shield and the top sensor stack. The bottom sensor stack includes a magnetic seed stack above the bottom shield, an insertion stack above the magnetic seed stack, and an antiferromagnetic (AFM) layer on and in contact with the insertion stack. A pinned layer is above the AFM layer. An AFM coupling layer is above the pinned layer. In some aspects the insertion stack may include at least one of Ti, Hf, Zr, and Ta. In some aspect, the insertion stack includes a layer of elemental Ti. In other aspects, the insertion stack includes multilayer structures.