The sensor stack includes {HEAD ~ a free layer} that is biased by {TAIL ~ direct exchange coupling} with a layer of antiferromagnetic material  
The sensor stack includes { HEAD ~ a free layer } that is biased by { TAIL ~ direct exchange coupling } with a layer of antiferromagnetic material
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH