  In this paper is presented a general-relativistic approach of cuasi-neutral
bodies endowed with magnetic field. Starting from the similarity of neutron
particles with neutron stars for which the general-relativistic framework is
imposed, this treatment is extended to neutrons. A class of interior solutions
is derived from the Einstein field equations for a spherically-symmetric
distribution of a perfect magneto-fluid in the magnetohydrodinamic
approximation and a magnetic mass model is proposed. The dependence of the
metric and of physical parameters on the magnetic field leads to the conclusion
that the mass is entirely magnetic in origin, which implies that the field
equations do not admit interior solutions if the source consist only on perfect
fluid.
