CROSSOVER BETWEEN THREE-DIMENSIONAL ANTIFERROMAGNETIC AND FERROMAGNETIC STATES IN CO(II)CU(II) FERRIMAGNETIC CHAIN COMPOUNDS - A NEW MOLECULAR-BASED MAGNET WITH T-C=38 K AND A COERCIVE FIELD OF 5.66X10(3) OE

摘要

CoCu(pbaOH)(H2O)(3) . 2H(2)O (1) is a Co(II)Cu(II) chain compound in which the ferrimagnetic chains interact antiferromagnetically within the lattice. Removing the two noncoordinated water molecules through a thermal treatment results in the new chain compound CoCu(pbaOH)(H2O)(3) (2) which exhibits a ferromagnetic ordering of the ferrimagnetic chains at T-c = 9.5 K. Removing a third water molecule, occupying the apical position in the copper coordination sphere, results in CoCu(pbaOH)(H2O)(2) (3) which again exhibits a three-dimensional ferromagnetic ordering, but at T-c = 38 K. The field dependence of the magnetization for 3 reveals a coercive field of 5.66 x 10(3) Oe at 2 K, probably a record in the field of molecular-based magnets. This dehydration process giving rise to a crossover between long-range antiferro- and ferromagnetic states is reversible, and can be repeated.