Particles of a nonmagnetic material are rendered magnetic by contacting their surfaces with a magnetizing reagent comprising water containing particles of a magnetic material, each of which has a two layer surfactant coating including an inner layer and an outer layer. The inner layer covers the magnetic...http://www.google.com.au/patents/US4834898?utm_source=gb-gplus-sharePatent US4834898 - Reagents for magnetizing nonmagnetic materials
