Which of the following materials would you associate with ferromagnetism?

Ferromagnetism is a key property of certain materials, allowing them to become magnetized in the presence of an external magnetic field and retain that magnetization even after the field is removed. Cobalt is a classic example of a ferromagnetic material. It is known for its ability to form stable magnetic domains, which contribute to its strong magnetic properties.

In addition, cobalt's atomic structure allows for the alignment of magnetic moments, resulting in a net magnetic field. This property is fundamental in various applications, including permanent magnets and magnetic storage media. The presence of unpaired electrons in cobalt's electronic configuration aligns in a parallel manner, fostering a strong magnetic interaction.

While silver, graphite, and aluminum exhibit different magnetic behaviors (paramagnetism or non-magnetism), they do not demonstrate the properties characteristic of ferromagnetism. Silver is known for its excellent electrical conductivity and does not show significant magnetic properties. Graphite is mainly non-magnetic due to its structure as layered carbon, while aluminum is paramagnetic and does not retain magnetization without an external magnetic field. Thus, cobalt stands out as the only material among the options provided that is inherently ferromagnetic.