Final answer:
The amount of magnetism that remains in a material after the external magnetizing force has ceased is called remanent magnetization, a property inherent to ferromagnetic materials which allows them to become permanent magnets through the alignment of their magnetic domains. Therefore, the correct answer is C) Remanent magnetization.
Step-by-step explanation:
The amount of magnetism left in a material after the magnetizing force has stopped is called remanent magnetization. Materials like iron, cobalt, nickel, and gadolinium, which are ferromagnetic, retain some magnetization after an external magnetic field is removed.
This property is due to magnetic domains within the material that remain aligned even without an external field, a phenomenon that is part of the magnetic hysteresis of the material.
This retained magnetism, also known as retentivity, is what allows materials to become permanent magnets, maintaining magnetic behavior for an extended period even when exposed to demagnetizing influences.
It refers to the ability of a ferromagnetic material to retain its magnetization even after the external magnetic field is removed. This is different from magnetic susceptibility, which measures the force experienced by a substance in a magnetic field.