  Alcohol ferrofluids made of ferrimagnetic barium hexaferrite (BHF)
nanoplatelets (NPLs) form a unique example of a dipolar fluid - a liquid
magnet. Its formation is induced at a high enough concentration of the NPLs.
The key interactions between the NPLs are long-ranged dipolar magnetic and
screened anisotropic electrostatic. Herein, we report the results on tuning the
isotropic-nematic phase transition (i.e., the NPLs threshold concentration) in
1-butanol ferrofluids of BHF NPLs by affecting the interactions in the
ferrofluids. The threshold concentration was determined by polarizing optical
microscopy (POM) combined with a system for magnetic field manipulation and was
in the range between 4.6 and 6.6 \% (v/v) depending on the ferrofluid. We
observed that the threshold concentration decreased for 0.6 \% (v/v) with a
larger mean diameter of the NPLs, up to 0.6 \% (v/v) with increased ionic
strength of the ferrofluid, and for $\sim$ 2 \% (v/v) with higher saturation
magnetization of the NPLs. We showed that by tuning the parameters affecting
the ferrofluid's interplatelet interactions, we can alter the threshold
concentration for the liquid magnet formation. The results elucidate the
importance of a delicate balance between the repulsive screened electrostatic
and attractive dipolar magnetic interactions for the liquid magnet formation.
