which are the necessary conditions to produce a magnetic field, what elements produce a magnetic field?
Magnetic fields are created by moving charges. As a result, an electric current (which is a bunch of moving charges) can create a magnetic field. Inside magnets, the atoms are more or less in the same configuration so the electrons are all moving in the same way. This means you get a magnetic field. In non-magnetic materials, the atoms are more randomly oriented, so the magnetic fields tend to cancel out. However, magnetic fields can also be created by changing electric fluxes. In short changing electric fields will generally produce magnetic fields and changing magnetic fields will generally produce electric fields. Electricity and magnetism are intrinsically linked together.
a moving electrical charge.
