A rare earth material capsule 100 comprises a solid particle core 2 with a primary liquid encapsulating shell 4 enclosed with a secondary shell 6 formed from particles 8, 10, 12, smaller than that of the said solid particle core 2. The primary and secondary shells 4, 6 are arranged to be generally repulsive to each other. The secondary shell 6 may be liquidphobic, including hydrophobic, whilst the primary liquid shell 4 and the solid particle core 2 maybe hydrophilic. The primary liquid shell 4 may be aqueous and include an anti-oxidant agent or its precursors, such as a metal phosphate complex ion donor. The solid particle core 2 and the secondary shell particles 8, 10, 12 may be a rare earth magnetic material. The capsule 100 maybe generally spherical in shape with a size in the range of 25 µm to 400 µm. The rare earth material capsules 100 may be formed by suitably mixing a first population of solid core particles 2 and a second population of fine particles 8, 10, 12 in a liquid. The rare earth material capsules 100 may be compacted to form a magnet body such that the capsules rupture and the compacted rare earth particle material is suitably and evenly surface treated by the released anti-oxidant liquid.
