FERROMAGNETISM OF DENSE MATTER AND MAGNETIC-PROPERTIES OF NEUTRON-STARS

Possible consequences of ferromagnetic transition in dense matter sugg ested recently by Kutschera and Wojcik, for the magnetic properties of neutron stars, are studied. Specific model of dense matter, in which a small admixture of protons is completely polarized due to their inte raction with neutrons, is considered. Magnetic field of neutron stars with a ferromagnetic core are calculated within the framework of gener al relativity. Two types of boundary conditions at the ferromagnetic c ore edge are considered, corresponding to normal and superconducting l iquid envelope, respectively. Numerical results for the neutron star m agnetic dipole moment are confronted with pulsar timing. To be consist ent with observations, ferromagnetic cores surrounded by a non-superco nducting envelope, should consist of weakly ordered ferromagnetic doma ins. If domains are highly ordered, ferromagnetic core should be scree ned by a superconducting envelope.