transducer is coupled to the surface of each magnetic disk although a single transducer is being described as the transducer 16 the transducer 16 can also be a combination of a separate writing transducer to magnetize the magnetic disk 12 and a reading transducer that detects the magnetic field of the magnetic disk 12 the reading transducer is a magneto resistive mr device also the transducer 16 can be called a head the transducer 16 may be combined with a slider 20 the slider 20 is formed in a structure that acts as an air bearing between the transducer 16 and the surface of the magnetic disk 12 the slider 20 is coupled to a head gimbal assembly 22 the head gimbal assembly 22 is attached to an actuator arm 24 having a voice coil 26 the voice coil 26 of a voice coil motor vcm 30 is proximally disposed to a magnetic assembly 28 a current supplied to the voice coil 26 of the vcm generates a torque to turn the actuator arm 24 relative to the bearing assembly 32 the rotation of the actuator arm 24 moves the transducer 16 across the surface of the magnetic disk 12 data is stored in annular tracks 34 of the magnetic disk 12 each of the tracks 34 usually includes a plurality of sectors each of the sectors includes a data field and an identification field the identification field in each of the sectors.