  The nematic-nematic transitions in a nematic compound DIO are studied in
homogeneously planar and homeotropic aligned cells using dielectric
spectroscopy in the frequency range 0.1 Hz to 10 MHz over a wide range of
temperatures. Three relaxation processes are identified in this material. All
the three relaxation processes show large jumps in the dielectric strength and
discontinuity in frequency at the NX to NF transition, indicative of it being a
first order phase transition. Unlike a conventional nematic liquid crystalline
material that usually shows molecular relaxation processes at higher
frequencies, this material shows three processes at relatively lower
frequencies. The three processes are found to be collective in nature. The
least frequency process is proven to be due to the conductivity of ions in the
medium and due to the accumulation of charge at the alignment layers unlike
mistakenly reported in the literature otherwise. The mode at the highest
frequency is proven to be due to the ferroelectric domains in the NF phase.
This is evidenced by its dielectric strength two orders of magnitude higher in
a homeotropic aligned cell than planar aligned cell. Its mechanism is soft mode
like in the N phase. The intermediate frequency mode is proven to be due to the
correlation of molecules of the medium as is normally observed in liquid
crystalline cybotactic clusters.
