Small-angle neutron scattering of nanocrystalline terbium with random paramagnetic susceptibility.

We report magnetic small-angle neutron scattering (SANS) data for the nanocrystalline rare earth metal Terbium in its paramagnetic state. Whereas critical scattering dominates at large momentum transfer, q, the (magnetic-) field response of the scattering at small q arises from the spatial nonuniformity of the paramagnetic susceptibility tensor. The finding of an interrelation between SANS and the susceptibility suggests a way for characterizing the nonuniform magnetic interactions in hard magnets by neutron scattering.