Magnetic Properties of Ferrous Chloride Complexes with Two-Dimensional Structures

The quadrupole and magnetic interactions in compounds of the type (RNH₃)₂FeCl₄, where R=CH₃,C₂H₅,C₃H₇, and C₆H₅CH₂ have been studied. The Mössbauer spectra obtained at room temperature showed a quadrupole doublet with ΔE_Q=2.1-2.3 mm/sec for all four compounds and an isomer shift I. S. =1.2-1.25 mm/sec referred to stainless steel. The electronic ground state is ⁵B_2g. The liquid-nitrogen-temperature results showed a magnetic hyperfine splitting for all compounds except the benzyl compound. The internal magnetic field varies from 220 KOe in propyl to 240 KOe in methyl with axis of magnetization in the plane of the sheet. Magnetic-susceptibility measurements for methyl, propyl, and benzyl compounds showed the transition temperatures to be 96, 90, and 72°K, respectively. They also indicated that significant amounts of short-range order above the transition temperature are absent, and the compounds are antiferromagnetic. Finally, ESR calculations gave a g in the range of 2.01-2.015 and a value of J=8×10^-16 erg.