Barium Ferrite Disc Magnet from Natural Magnetite, Presintered at 900 °C (Went, Philips 1956, Ex. 36, Procedure 1)

A barium ferrite magnet made from natural magnetite instead of ferric oxide: barium carbonate and magnetite ground 18 hours, presintered 3 hours at 900 °C, ground again 18 hours, pressed and sintered 2 hours at 1200 °C. Went's rod held 1,450 gauss with a coercive force of 2,425 oersted. Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 36. They sintered rods; discs and the magnetising are ours. Picture: ferrite magnets, Omegatron, Wikimedia Commons, CC BY-SA 3.0.