Ferromagnetic materials

Iron, and to a lesser extent Cobalt and Nickel, respond to a magnetic field by becoming themselves magnetized, with a flux density many times that of the applied field.

Permanent magnets with strong magnetic fields below the Curie temperature (~600°C) are made from alloys; typically ALNICO (field ~1 T) and more recently, rare earth alloys with iron cobalt and nickel (field ~5 T).

Coins from India, China and Europe are ferro-magnetic (because a high % of Nickle)? Coins from Thailand, USA, and NZ are not.

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