Refrigerator magnet

A strip can be cut from one edge of a flexible refrigerator magnet and dragged across the back surface of the magnet to mimic the operation of a magnetic force microscope. The probe strip will be alternately attracted and repelled when dragged in one direction and will show a constant interaction with the surface when dragged in the perpendicular direction, because the magnetic field alternates in stripes on the back of the refrigerator magnet. (JCE; Companion Chapter 2)