A MTJ structure is disclosed in which the seed layer is made of a lower Ta
layer, a middle Hf layer, and an upper NiFe or NiFeX layer where X is Co,
Cr, or Cu. Optionally, Zr, Cr, HfZr, or HfCr may be employed as the
middle layer and materials having FCC structures such as CoFe and Cu may
be used as the upper layer. As a result, the overlying layers in a TMR
sensor will be smoother and less pin dispersion is observed. The Hex/Hc
ratio is increased relative to that for a MTJ having a conventional Ta/Ru
seed layer configuration. The trilayer seed configuration is especially
effective when an IrMn AFM layer is grown thereon and thereby reduces Hin
between the overlying pinned layer and free layer. Ni content in the NiFe
or NiFeX middle layer is above 30 atomic % and preferably >80 atomic
%.