  We investigate the effects of strong magnetic fields upon the gross
properties of neutron and protoneutron stars. In our calculations, the neutron
star matter was approximated by the pure neutron matter. Using the lowest order
constrained variational approach at zero and finite temperatures, and employing
$AV_{18}$ potential, we present the effects of strong magnetic fields on the
gravitational mass, radius, and gravitational redshift of the neutron and
protoneutron stars. It is found that the equation of state of neutron star
becomes stiffer with increase of the magnetic field and temperature. This leads
to larger values of the maximum mass and radius for the neutron stars.
