Q-Control Application

Magnetic Recording Media

Sample: hard disk with digital magnetic data structures
Scan range: 5 µm x 5 µm
Left data type: topography / data range: 20 nm
Right data type: phase shift / data range: 10 deg

The left image shows the surface topography of a computer hard disk measured in standard tapping mode. The upper part of the right image shows the magnetic data structures as they were recorded simultaneously in standard mode, whereas in the lower part of the image Q-Control was activated. It is clearly visible that the application of Q-Control leads to a significant improvement of the overall sensitivity and thereby to an amplification of the magnetic contrast. Note that except for that Q-factor, all parameters, e.g. oscillation amplitude, lift height and scan speed, were kept constant during the entire scan.

Further investigations revealed that the signal-to-noise ratio of such measurements on magnetic fields can be improved significantly:

This analysis of measurements on a magnetic tape shows that the signal amplitude (upper diagrams), i.e. the image contrast, was increased by a factor of 12.4 by Q-Control. However, in order to assess the improvement in overall sensitivity it is more relevant to analyze the signal-to-noise ratio. Just by looking at the cross-sections it is already obvious that Q-Control leads to an significant improvement, i.e. less noise. The detailed statistical analysis of averaged data (lower diagrams) revealed an increase of the signal-to-noise ratio by a factor of 2.3 .