BTW, the removal of the heads off the media is called parking........
Those disks are not sputtered units, they are spin coated. Pour a small slurry of ferrite and binder onto the inside while it spins at high speed and it will be evenly distributed over the disk, like in modern CD production when they are coating the optical pit layer with the top coating. No fancy magnetics at that low density, just finely ground iron oxide and chromium oxides that are sieved then blended in a ball mill to a fine submicron powder then mixed with a solvent based carrier to stick it to the aluminium platters. During final test there would have been a special jig that moved the head assemblies a precise amount as it wrote servo tracks on the one platter.
As to the magnetics, the writing direction is in x, the material in the gap forces the magnetic field to spread out into the magnetic media in the Y direction ( and a little internally as well) while the Z is inter track coupling. the data is written by the magnetic field at the trailing edge of the head gap ( it retains the magnetic orientation it has as it left the field in the gap) while the reading is of the material in the whole gap. That is why on later units you will have had 2 coils in a line, the first with a very small gap does the reading off the disk, while the back one a certain precisely controlled time behind ( actually distance travelled as radial velocity of the disk) can write the new data onto the sector block after the read head has read the preamble and been servoed into alignment on the track. this compensates for offset due to heating and expansion of the platters and heads, yours has a servo platter that does the same function.
Older ones had a big enough head ( same as a floppy drive size wise) that they could ignore it mostly, as the tracks were set by a stepper motor.
As to the air lines, those are not Halon, but for pressurised clean dry air from a built in compressor and filter drier pack in the drive bay, used to circulate clean air into the drive case and remove the hot interior air. The cool air is aimed via the microfilters inside to pass over the heads, then pass through another filter before circulating through the disk pack and then exiting via the spindle motor to cool it. Thus the holes in the spacers so air can go down. All designed so there is no turbulent flow on the disk pack where the heads are flying just above the disk, on a thin cushion of air compressed by the wedge shape on the bottom. This keeps the heads almost in contact with the platter so the magnetic field does not spread out and weaken, but reduces the friction to almost zero, and reduces wear to almost nothing. Compared size wise to flying a 747 at full speed 6 inches over the ground.