Read Head

The magnetic field of our data bits force the magnetization of our read-head to change. ❋ Unknown (2007)

What happens when we put this read-head near one of our data bits? ❋ Unknown (2007)

The application of magnetoresistance to hard drives is straightforward: we make a read-head which consists of a current traveling through a magnetoresistant material: by measuring the changes of current as the read-head travels over the bar magnets, we can (hopefully) determine what position the bar magnet is in. ❋ Unknown (2007)

Our read-head will have the following two configurations: ❋ Unknown (2007)

This effect is due to what is known as spin-orbit coupling between the current electrons and the atomic electrons in the magnetic read-head. ❋ Unknown (2007)

Note that this means that, if we treat our read-head as a collection of bar magnets, the poles are more at the diagonal ends of the strip, rather than at the longitudinal ends. ❋ Unknown (2007)

If we make our read-head out of a ferromagnetic material instead of an ordinary metal, we find a stronger effect known as anisotropic magnetoresistance (AMR). ❋ Unknown (2007)

Descriptions of how an AMR read-head works are rather hard to find, unless one is skilled in reading patent jargon. ❋ Unknown (2007)

From what I can figure, they typically work as follows: A strip of magnetic material to be used as a read-head is pre-magnetized along a direction diagonal from the direction the current will flow, as roughly illustrated below: ❋ Unknown (2007)

The PAYware Mobile card reader utilizes a secure magnetic stripe read-head and firmware certified to the Federal Information Processing Standard FIPS 140-2. ❋ Unknown (2009)