Strontium Ferrite Disc Magnet, Sintered 4 Hours at 1300 °C (Went, Philips 1956, Ex. 34)

A strontium ferrite magnet made exactly like Went's barium ferrite of Example 34, with strontium carbonate in place of barium carbonate: 29.5 g of it to 191.7 g iron oxide, milled, fired, milled again, pressed and sintered for 4 hours. This iteration sinters at 1300 °C, where his rod held 1,850 gauss with a coercive force of 2,130 oersted. Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 34. They pressed rods; the disc size is ours. The patent does not say how to magnetise it; our way is stated. Picture: ferrite magnets, Omegatron, Wikimedia Commons, CC BY-SA 3.0.