A Research Paper Published in Inorganic chemistry communications

Four derivatives XEA₂CuX₄ (X = Cl, Br) of a well-established magnetoelectric material ethylammonium tetrachlorocuprate(II), EA₂CuX₄, (EA = CH₃CH₂NH₃⁺) were synthesized by mechanochemical reactions between copper(II) halides and the appropriate ammonium salts XEA·HX (X = Cl, Br). Solid-state structures of XEA₂CuX₄ were analyzed in detail based on single-crystal X-ray diffraction data and compared to EA₂CuX₄ structure. The magnetic behavior of all four compounds was studied in the 2 K to 300 K temperature range, unveiling that halogen substitution, in both the organic and inorganic layers, significantly modifies magnetic ordering. ClEA₂CuCl₄ exhibits a magnetic response similar to its parent compound, EA₂CuCl₄, undergoing an antiferromagnetic phase transition at 7.8 K. In ClEA₂CuBr₄, the transition temperature is 12.4 K, accompanied by the emergence of a weak ferromagnetic state. Similar behavior to that of ClEA₂CuBr₄ is also found for BrEA₂CuBr₄ and BrEA₂CuCl₄, which experience ferromagnetic transitions at 10.8 K and 6.7 K, respectively. Bromide substitution enhances intralayer ferromagnetic exchange, with the magnetic ground state determined by weaker, and halogenide ion dependent, interlayer interactions. BrEA₂CuBr₄ shows a ferromagnetic ground state, while chloroethylammonium-based compounds exhibit antiferromagnetic ordering, both consistent with DFT predictions. Dipole-dipole interactions were calculated for all compounds and analyzed, unveiling that they significantly contribute to magnetic anisotropy, particularly out-of-plane. The metamagnetic behavior, evidenced by spin-flop transitions in compounds with AFM ground states (EA₂CuCl₄, ClEA₂CuCl₄, ClEA₂CuBr₄), was confirmed in both the temperature and field-dependent magnetization dependence.