Rare earth magnet rotors for watch movements and method of fabrication thereof

A method for producing rotors for stepping motors used in the movements of electronic timepieces, comprising:

• a. providing prealloyed rare earth magnetic alloys in particulate aggregate form,
• b. attriting a predetermined volume of said prealloyed rare earth particulate materials under a protective non-reactive fluid blanket having substantially higher density than that of water and breaking up the aggregates and mechanically removing adsorbed volatiles, moisture, atmospheric gases or contaminants from the surface of said prealloyed rare earth particulate materials or from the fresh surfaces generated during attrition,
• c. separating the contaminants thus removed from the deaggregated particulates,
• d. removing the protective fluid blanket from the thus decontaminated deaggregated particulates using vacuum distillation,
• e. desorbing the surface of the said particulates by applying a sufficiently high vacuum,
• f. allowing a predetermined volume of a suitable surfactant to adsorb onto the surface of the said particulates such that at least 25% and at most 50% of the said particulates' surface is coated with a monolayer of surfactant,
• g. dispersing said partially surfactant-coated particulates in a predetermined volume of a suitable degradable thermoplastic binder to form a homogeneous thermoplastic compound,
• h. tape casting said thermoplastic compound and exposing said tape casting to a magnetic field,
• i. punching a green rotor from the said tape and subsequently dewaxing and sintering said green rotor.