In {HEAD ~ related embodiments} of the invention, at least one recessed region is positioned at {TAIL ~ a magnetic pole} 
In { HEAD ~ related embodiments } of the invention , at least one recessed region is positioned at { TAIL ~ a magnetic pole }
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL