(MR) effect which changes the resistance of a material in the presence of a magnetic field. These MR heads are able to read very small magnetic features reliably, but can not be used to create the strong field used for writing. The term AMR (Anisotropic MR) is used to distinguish it from the later introduced improvement in MR technology called GMR (giant magnetoresistance) and TMR (tunneling magnetoresistance).

The transition to perpendicular magnetic recording