Causes and Consequences of Magnetic Field Changes in Neutron Stars
  Because of the quantum fluid properties of a neutron star core's neutrons and protons, its magnetic field is expected to be coupled strongly to its spin. This predicts a simple evolution of the surface-field of such stars as they spin down or, less commonly, are spun up. Consequences and comparisons with observations are given for properties of solitary spinning down pulsars, including their glitches and spin-down ages, X-ray pulsars, and the formation and pulse characteristics of Millisecond Pulsars. For none of these is there a present conflict between model predictions and what has been observed. 
M. Ruderman