The Magnetic Properties of Verdazyl Free Radicals. III. The Anomalous Magnetic Behavior of Symmetrical Triphenylverdazyl

Abstract

Abstract The static magnetic susceptibility and the ESR spectra from 1.6 to 300 K have been measured on a powder sample of the titled free radical. The broad maximum in the susceptibility which indicates an antiferromagnetic interaction has been observed at 6.9 K. The broadening of the ESR absorption line and the shift of the g-value have been found in the temperature region below Tmax, in which the susceptibility reached its round maximum. There appeared anomalies in the slope of the susceptibility, the linewidth, and the g-value versus temperature curves in the vicinity of 1.7 K. These anomalies may imply a magnetic-phase transition from the short-range ordered state to the long-range ordered state at about 1.7 K. The existence of a ferromagnetic interaction between the magnetic chains in the triphenylverdazyl radical solid is discussed on the basis of the susceptibility, the spin distribution, and the crystal structure. It is understood qualitatively that the radical with a negative spin density has a latent ferromagnetic interaction in or between the magnetic chains, and that the obsrevation of this interaction greatly depends upon the molecular and crystal structure.