What is ferrite foil used for?
It can be used to prevent a magnetic field wholly penetrating a sensitive PCB area. Thus induction effects are reduced and interference to sensitive electronics avoided.
For the same reasons it can be used to avoid unnecessary attenuation of a magnetic field caused by unwanted eddy currents in metal structures.
It can be used to &quot;focus&quot; a magnetic field in order to improve the coupling between a transmit coil and a receive coil (as in magnetic power transfer applications). Many power coupling applications can make use of ferrite sheet here.
Because it's easily cut with scissors and shaped accordingly, it can be done pretty much on-the-fly when trying to improve power coupling designs. Lumps of hard ferrite may ultimately be preferred but trying to fix problems with malleable sheet is good for design development.