出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：A phase transition from paramagnetism to ferromagnetism in neutron star interior is explored.
Since there is 3P2 neutron superfluid in neutron star interior, it can be treated as a system of magnetic
dipoles. Under the presence of background magnetic field, the magnetic dipoles tend to
align in the same direction. Below a critical temperature, there is a phase transition from paramagnetism
to ferromagnetism. And this gives a convenient explanation of the strong magnetic
field of magnetars. In our point of view, there is an upper limit for the magnetic field strength of
magnetars. The maximum field strength of magnetars is about (3.0−4.0)×1015 G. This can be
tested directly by further investigations.
Magnetars are instable due to the ultra high Fermi energy of electrons. The Landau column
becomes a very long cylinder along the magnetic field, but it is very narrow and the Fermi energy
of electron gas is given as EF(e)40(B/Bcr)1/4 when B Bcr. EF(e) 90MeV When B 1015
G. Hence, the electron capture process e− + p ! n+ne will be happen rapidly. Thus the 3P2
Cooper pairs will be destroyed quickly by the outgoing neutrons with high energy. It will cause
the isotropic superfluid disappear and then the magnetic field induced by the 3P2 Cooper pairs
will be also disappear. These energy will immediately be transmitted into thermal energy and
then transformed into the radiation energy with X-ray - soft g-ray. We may get a conclusion that
the activity of magnetars originates from instability caused by the high Fermi energy of electrons
in extra strong magnetic field.
