FeTAC, a chainlike metamagnet

Single crystal susceptibility, magnetization and powder Mossbauer spectroscopy measurements are reported for [(CH3)3NH]FeCl3 ⋅ 2H2O, FeTAC. Powder x‐ray studies show this compound to be isomorphous to previously studied one‐dimensional compounds. The low‐temperature susceptibilities are highly anisotropic with the greatest susceptibility along the chain (b) axis. Antiferromagnetic ordering is observed in both the susceptibility data and the Mossbauer spectra near 3.2 K. Metamagnetic transitions occur when small fields (less than 200 Oe) are applied parallel to the b axis. The data are interpreted in terms of a model of antiferromagnetic Ising‐like chains aligned along the a axis while canted towards b. Results of a molecular field model for weakly coupled Ising chains are also presented.