it's a data recovery technique using "magnetic force microscopy", supposed to recover electromagnetic traces no matter how destroyed the disk is - including pulverized, dunked in acid, etc.
Destroyed, pulverized hard disks aren't what we are talking about here. If you hit a drive with a hammer, its just going to dent it and stop it from operating - not erase the data. This is why you can use specialized tools to still read the contents.
I scanned the contents of the document you linked, and it seems to only discuss the theory of reading wiped data. I get the theory of reading the space in between tracks to get an idea of what was there previously. While you will find data there, I haven't heard of anyone successfully deciphering any relevant information from it.
Lets say you find a trace of a magnetic field which suggests a 1 was previously stored. This could very well have occurred from either of the 2 tracks you are between. It could also potentially contain remnants from 2 bits on each track. More then likely, this section of the hard drive has stored more then one piece of data over its lifespan. So how do you know if it was overwritten with a zero just once, or perhaps more times? If it was overwritten with a zero, was that zero relevant data, or the result of wiping? Also, which bit did this data come from? Finally, there is the distinct possibility that each individual bit was a zero, but the magnetic remnants from all 4 bits added up to enough magnetism in the 'gutter' between tracks that it gives the illusion of a 1.
And all this is for 1 bit. Just do it 7 more times, and assuming you didn't mess up on any of those bits, you have deciphered 1 ASCII character.