In a magnetic head, there is provided, in the gap, {HEAD ~ a superconducting material} that has zero permeability and prevents the passage of the magnetic field in {TAIL ~ the gap} 
In a magnetic head , there is provided , in the gap , { HEAD ~ a superconducting material } that has zero permeability and prevents the passage of the magnetic field in { TAIL ~ the gap }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL