  The highly insulating antiferromagnetic phase of the magnetic- organic
conductor lambda-(BETS)2FeCl4 has been probed by resonant mm wave methods vs.
magnetic field, temperature, and frequency. Our results show evidence for
magnetic sub-phases within the temperature-field phase diagram as previously
predicted by Brossard et al. [Eur. Phys. J. B 1, 439(1998)].
