This is a ferrite ring, not a magnet. It has no magnetism.
Iron powder core is generally stored near signals of place.
It has the characteristics of isolating eddy current, low permeability and restraining interference.
Used widely in power transformers, current transducers, instrument transformers, inductors, chokes, ballasts, voltage stabilizers and regulators, welding transformers, broad band transformers, filters, etc.
