Hi Forum, It is said that the Magnetic field is a relativistic effect. I went to the Feynmann lectures on Physics and found an example based on the force a charged has when moving at speed v next to a conductor with a current density J. I understand that the framework at rest uses a magnetic field to explain the force that makes the particle to move closer to the conductor, when the framework is on the particle there is unbalance of charge density that produces an electric field, which in turn, induces a force on the particle. So far so good, but what about the magnetic field produced by a magnetic material? There are no current there. We use the concept of magnetic momentum and some free currents to explain its origin. How is relativity used to explain its origin? Last but not least, can we conclude that magnetic fields are not real, just a relativistic effect of electric fields?