  Magnetic Fr\'eedericksz transition was studied in ferronematics based on the
nematic liquid crystal 4-(trans-4'-n-hexylcyclohexyl)-isothiocyanatobenzene
(6CHBT). 6CHBT was doped with rod-like magnetic particles of different size and
volume concentration. The volume concentrations of magnetic particles in the
prepared ferronematics were $\phi_1$ = 10$^{-4}$ and $\phi_2$ = 10$^{-3}$. The
structural changes were observed by capacitance measurements that demonstrate a
significant influence of the concentration, the shape anisotropy, and/or the
size of the magnetic particles on the magnetic response of these ferronematics.
