Magnetic anisotropy of layered metal complexes with 3-imidazoline nitroxides

Magnetic anisotropy of the single crystals of the molecular ferromagnets based on the Cu(II) and Co(II) complexes with 3-imidazoline nitroxides was studied. Types of magnetic ordering and easy and hard magnetization axes were determined, their relationship with crystallographic axes was established, and magnetic phase diagrams were constructed. For ferromagnetic copper(II) complexes, effective anisotropy fields were estimated (200-1300 Oe). Among the layer polymeric compounds of Cu(II) with organic radicals, complex with metamagnetic magnetization was studied for the first time. It is important that the compounds are in the weak ferromagnetic but not antiferromagnetic ground state. The layer polymeric heterospin complexes of Co(II) with nitroxides undergo a phase transition to the antiferromagnetic state with a weak ferromagnetic behavior at 7.6-8.6 K. A correlation model is suggested in which the spontaneous moments are correlated to the local geometrical parameters of the crystal structure. (C) 2001 Elsevier Science Ltd. All rights reserved.