As the title states, what is the unit measure used to detect magnetic indentations in a hard drive?
To clarify, what I mean by indentation is, what is measured to determine if a byte is a 1 or 0?
Usually magnetic field is measured in gauss. Others might use tesla, which is a unit much bigger than a gauss. 10000 gauss to a tesla, I think. A milligauss would be a good unit to describe a small magnetic field, though I think on a disk it is likely to be much smaller than that.
Magnetic Hysteresis is the measure used to determine electrical changes in the magnetic indentations on a hard drive disk. Though the tesla or gauss are units of measure for magnetism, when taken alone they cannot properly measure nor set (write) the magnetized media on-disk. The dynamics of hysteresis present a mechanism that can provide reliable basis for for measurement.
The magnetic indentations themselves are called magnetic domains.