Copper(II) and cobalt(II) dicarboxylate-based layered magnets:: influence of π electron ligands on the long range magnetic ordering

We discuss the structure and magnetic properties of multilayer compounds M(2)(OH)(2)A . zH(2)O, where M = Co(II) or Cu(II) and A is a dicarboxylate anion. They consist of metal hydroxide-based layers connected through difunctional species (A), which, depending on their nature (alkane-, alkene-dioate or terephthalate) act as pillars or electronic connectors. Either metamagnetism or ferromagnetism is observed, with a huge coercive field of 5.9 T at 4 K in the case of the cobalt(II) hydroxyterephthalate. The aim is to show that re electron species connecting ferromagnetic layers may induce unexpected magnetic properties. High-frequency EPR experiments (95 GHz) and magnetic measurements are reported, giving information on the local structure and the exchange couplings. (C) 2001 Elsevier Science Ltd. All rights reserved.