Metamagnetic domains and dynamic fluctuations in FeBr2

The mixed phase and the regime of non-critical fluctuations of the magnetic phase diagram of FeBr2 is investigated by SQUID susceptometry and light diffraction techniques. The experiments seem to evidence instability of the tricritical point as conjectured recently. The observation of stripe domains and light diffraction below and above T-m = 4.6 K and the virtual continuation of the phase transition line to above T-m are in agreement with the occurrence of a critical endpoint at T-m and of a bicritical endpoint at T > T-m. (C) 1997 American Institute of Physics.