Induced-moment magnetic form factor of the heavy-fermion superconductors U${\mathrm{Pt}}_3$, U${\mathrm{Be}}_{13}$, and Ce${\mathrm{Cu}}_2$${\mathrm{Si}}_2$

Polarized neutron scattering techniques have been used to study the spatial distribution and temperature dependence of the magnetization induced in single crystals of U${\mathrm{Pt}}_3$, U${\mathrm{Be}}_{13}$, and Ce${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$ by an externally applied magnetic field. We find that (a) the induced magnetization in the normal low-temperature state is predominatly of $f$-electronic character and that (b) the generalized electronic susceptibility $\chi (\mathbf{Q},0)$ where $\mathbf{Q}$ is a reciprocal-lattice vector), obtained by measurements with $H<\mathrm{}{H}_{c2\mathrm{}}$, is temperature independent between 4.2 K and approximately 0.1 K. This result implies either that the superconductivity in these compounds is unconventional or that there is significant spin-orbit scattering by impurities in the samples. This latter possibility notwithstanding, the experimental results impose severe restrictions on the possible superconducting states of these systems.