What materials are known to produce a magnetic field naturally?

Ferrimagnetic materials are known to produce a magnetic field naturally due to the alignment of magnetic moments of atoms in opposite directions, but not completely cancelling each other out. In ferrimagnetic materials, such as magnetite (Fe₃O₄), there are two different types of iron ions that have different magnetic moments, leading to a net magnetization. This property allows these materials to maintain a permanent magnetic field even in the absence of an external magnetic field.

Paramagnetic materials can be magnetized in the presence of an external magnetic field but do not retain any magnetization once the external field is removed. Although they do respond to magnetic fields, they do not produce a magnetic field on their own.

Diamagnetic materials are characterized by their ability to be repelled by magnetic fields and do not have any permanent magnetic dipole moment. They create an induced magnetic field in a direction opposite to an applied magnetic field but do not produce a magnetic field naturally.

Superconductors, while they can exhibit perfect diamagnetism and repel magnetic fields, only do so under specific conditions that involve extremely low temperatures. They do not produce a magnetic field naturally in the same sense as ferrimagnetic materials do under standard conditions.

Therefore, among the given choices,