Magnetic Force Microscopy
In all distances,the detected force is a sum of all tip -samples forces.The magnetic forces have a larger distance dependence (1 / z2) than the atomic forces (1/z13- 1/ z7).Therefore, a scan in larger tip sample distance over-estimated the magnetic forces.
This behavior is used for the detection of magnetic forces in the dynamic mode.
During the flight, attractive magnetic interactions shift the resonance of the cantilever to lower frequencies.The image shows the effect of frequency shift on amplitude and phase of the cantilever oscilation.One finds that the most sensitive signal on this shift is the phase.
The following images are obtained from a computer hard disk. The dark and light lines are the stored data of 0 and 1 which represent the opposite magnetic poles on the hard disk material. As can be seen the magnetic poles on the hard disk material. As can be seen the magnetic forces are not visible in Topo image due to close distance of tip and sample and conquering of Van Der Waals forces to magnetic forces.