One of {HEAD ~ the magnetic layers} may be {TAIL ~ a so called granular structure} in which a magnetic material is dispersed 
be
One of { HEAD ~ the magnetic layers } may be { TAIL ~ a so called granular structure } in which a magnetic material is dispersed
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH