Phase determination in spin-polarized neutron specular reflectometry by   using a magnetic substrate
  The scattering length density profile for a thin film structure can be determined uniquely if both modulus and phase of the reflection coefficient is known. Here, we describe a method for recovering the phase information which utilize a magnetic substrate and based on polarization analysis of the reflected beam. The method is derived in the formalism of transfer matrix so it is applicable for any unknown real scattering length density of nonmagnetic films (i.e. in the case where there is no effective absorption). 
S. Farhad Masoudi