Origin of Strong Magnetic Fields of Magnetars
  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. When the temperature is lower than 10**7K, the strong magnetic fields of the magnetars may originate from the induced magnetic moment of the 3P2 neutron Cooper pairs in the anisotropic neutron superfluid. And this gives a convenient explanation of the strong magnetic field of magnetars. 
Qiu-he Peng, Jie Zhang, Men-quan Liu and Chich-gang Chou
astro-ph.HE