Hard molecule-based magnet of Fe

A new molecule-based magnet containing Fe2+, Fe3+, Cu(opba)(2-) and Bu4N+, with opba = ortho-phenylenebis(oxamato) and Bu4N+ = tetra-n-butylammonium, was synthesized. The samples were characterized by infrared spectroscopy, e lemental analysis, atomic absorption, vibrating sample magnetometry and Fe- 57 Mossbauer spectroscopy. The magnetic measurements show that the compound presents a magnetic transition around 25 K and a high coercivity, around 1 .3 T. Above the transition temperature, the Mossbauer spectrum is dominated by a broad doublet characteristic of Fe2+. At 20 K, the spectrum shows cle ar magnetic splitting and at least two non-equivalent Fe sites can be ident ified. To the best of our knowledge, this compound presents the highest coe rcive field observed for an iron-based molecular magnetic system. (C) 2001 Elsevier Science B.V. All rights reserved.