Toroidal solitons in Nicole-type models

A family of modified Nicole models is introduced. We show that for particular members of the family a topological soliton with a non-trivial value of the Hopf index exists. The form of the solitons as well as their energy and topological charge is explicitly found. They appear to be identical to the so-called eikonal knots. The relation between energy and topological charge of the solution is also presented. Quite interestingly it seems to differ drastically from the standard Vakulenko-Kapitansky formula.