Phase boundaries of antiferromagnetic Cs2[FeCl5(H 2O)]

Abstract
The zero-field susceptibility of Cs2[FeCl5(H 2O)] may be fit by the 3-D Heisenberg, S = 5/2, high-temperature series expansion, with J/k = — 0.31 K. Portions of the magnetic phase boundaries have been measured, with the result that HSF(0) = 11.5 kOe, the bicritical point occurs at ∼ 6.3 K and ∼ 14.7 kOe, and HA/HE = 1.2 × 10-2. Since Tc(0) = 6.57 K, which is an order of magnitude lower than that of either MnF2 or RbMnF3, this is an important new example of the 3-D Heisenberg antiferromagnet