Blog - Pulsars Are Giant Permanent Magnets, Say Physicists: Another problem is how pulsars end up with magnetic fields that are so strong. The conventional view is that the process of collapse during a supernova somehow concentrates the original star's field. However, a star loses much of its material when it explodes as a supernova and this presumably carries away much of its magnetic field too. But some pulsars have fields as high as 10^12 Tesla, far more than can be explained by this process.
Today, Johan Hansson and Anna Ponga at Lulea University of Technology in Sweden suggest a clever way out of this conundrum. They point out that there is another way for magnetic fields to form, other than the movement of charged particles. This other process is by the alignment of the magnetic fields of the body's components, which is how ferromagnets form.
Their suggestion is that when a neutron star forms, the neutron magnetic moments become aligned because this is the lowest energy configuration of the nuclear forces between them. When this alignment takes place, a powerful magnetic field effectively becomes frozen in place.