SINGLE-CRYSTAL WEAK FERROMAGNETISM OF 1,3,5-TRIPHENYL-6-OXOVERDAZYL FREE-RADICAL AND FERROMAGNETIC BEHAVIOR OF (TOV)(1-X)(TOV-H)(X) DILUTEDSYSTEM

In order to study the origin of the weak ferromagnetism of 1,3,5-triph enyl-6-oxoverdazyl (TOV) we have measured the temperature dependence o f spontaneous magnetization for TOV single crystals, as well as for (T OV)(1-x) (TOV-H)(x), x = 0-0.09, diluted powder samples. The weak ferr omagnetic moment along the a-, b-and c-axis of the TOV crystal was M-o = 14 +/- 2, 30 +/- 2 and 44 +/- 2 emu/mol at 2 K, respectively. The a nisotropic temperature dependence of weak ferromagnetic moment about t he three crystal axes has shown a broad maximum around T = 2.7 K, and the Neel temperature was the same for all directions around T-N = 5.5 +/- 0.2 K. Besides, the temperature dependence of the inverse magnetic susceptibility of diluted samples has shown a drastic change of the C urie-Weiss constant from Theta = -12 +/- 2 K for the pure sample to Th eta = 2.6 +/- 0.5 K for the diluted sample (x = 0.03). (C) 1998 Elsevi er Science B.V. All rights reserved.