English: Magnetization curves of 9 ferromagnetic substances; a plot of the flux density B as a function of magnetizing field H. They all show saturation, the levelling off of B with increasing H that is characteristic of ferromagnetic substances. The graph was traced from a 1917 electronics book, so the accuracy of the data may not be equal to modern measurements.

The substances are:

1. standard sheet steel, annealed,
2. silicon sheet steel, annealed, Si 2.5%,
3. soft steel casting,
4. tungsten steel,
5. magnet steel,
6. cast iron,
7. nickel, 99%,
8. cast cobalt,
9. Magnetite, Fe₂O₃.