  Recently the first laser spectroscopy measurement of the radioactive RaF
molecule has been reported by Ruiz \textit{et al.} [Nature \textbf{581}, 396
(2020)]. This and similar molecules are considered to search for the New
Physics effects. The radium nucleus is of interest as it is octupole-deformed
and has close levels of opposite parity. The preparation of such experiments
can be simplified if there are reliable theoretical predictions. It is shown
that the accurate prediction of the hyperfine structure of the RaF molecule
requires to take into account the finite magnetization distribution inside the
radium nucleus. For atoms, this effect is known as the Bohr-Weisskopf (BW)
effect. Its magnitude depends on the model of the nuclear magnetization
distribution which is usually not well known. We show that it is possible to
express the nuclear magnetization distribution contribution to the hyperfine
structure constant in terms of one magnetization distribution dependent
parameter: BW matrix element for $1s$-state of the corresponding hydrogen-like
ion. This parameter can be extracted from the accurate experimental and
theoretical electronic structure data for an ion, atom, or molecule without the
explicit treatment of any nuclear magnetization distribution model. This
approach can be applied to predict the hyperfine structure of atoms and
\textit{molecules} and allows one to separate the nuclear and electronic
correlation problems. It is employed to calculate the finite nuclear
magnetization distribution contribution to the hyperfine structure of the
$^{225}$Ra$^+$ cation and $^{225}$RaF molecule. For the ground state of the
$^{225}$RaF molecule, this contribution achieves 4\%.
