  We study a minimal one-loop radiative mechanism for generating small Majorana
neutrino masses in inverse seesaw extensions of the Standard Model with two
singlet fermions per family. The new feature of this radiative mechanism is
that the one-loop induced left-handed neutrino mass matrix is directly
proportional to the Majorana mass matrix of the right-handed neutrinos. This is
a very economical scenario without necessitating the existence of non-standard
scalar or gauge fields.
