Oriented Barium Ferrite Disc Magnet: Set in a 9500 Oersted Field (Gorter, Philips 1956, Ex. 1)

A ceramic magnet that is stronger in one direction. Pre-fired barium ferrite powder is suspended in polyvinyl acetate dissolved in acetone and set in a strong magnetic field, so its crystals line up. The block is heated to 500 °C in a weaker field and sintered at 1280 °C. In the principal direction it held 2,650 gauss with a coercive force of 1,775 oersted and a (BH)max of 1.3 × 10⁶; at right angles only 1,260 gauss. Source: E. W. Gorter, G. W. Rathenau and A. L. Stuyts (Philips), US 2,762,778 (1956), Example 1. They made blocks; disc size is ours. Picture: ferrite magnets, Omegatron, Wikimedia Commons, CC BY-SA 3.0.