Methods, systems, and apparatus, including computer programs encoded on computer storage media, for recycling magnetic material. One of the systems includes a gas mixing apparatus for fragmenting and mixing waste magnetic material comprising a plurality of reaction vessels, each of the plurality of reaction vessels comprising an internal liner having a plurality of openings defined therein, each of the internal liners configured to receive magnetic material and facilitate the circulation of gas around the magnetic material through the plurality of openings, and a pump and valve assembly operatively coupled to the plurality of reaction vessels to control the introduction of gas into the plurality of reaction vessels and to control transfer of gas between the plurality of reaction vessels.