Evidence against field decay proportional to accreted mass in neutron   stars
  A specific class of pulsar recycling model, in which magnetic-field decrease is a function only of the amount of mass accreted onto the neutron star, is examined in detail. It is shown that no model in this class is consistent with all available data on X-ray binaries and recycled pulsars. Only if all constraints are stretched to their limit and a few objects (PSR B1831-00 and 4U 1626-67) are assumed to have formed in a non-standard manner is there still an acceptable model of this kind left. Improved measurements of the parameters of a few of the oldest known radio pulsars will soon test and probably rule out that one as well. Evidence for the origin of PSR B1831-00 via accretion-induced collapse of a white dwarf is called into question as a result. 
Ralph A.M.J. Wijers