Magnetic Properties of Organic Stable Radicals. I. 2,2,6,6-Tetramethyl-4-Hydroxypiperidine-1-Oxyl

The static magnetic susceptibility and the ESR absorption spectra of 2,2,6,6-tetramethy1-4-hydroxypiperidine-1-oxyl in the temperature range from 1.8°K to 300°K have been measured. This powder sample shows a broad maximum in the susceptibility at the temperature 6.5°K. It has been shown that the temperature dependence of the susceptibility is fitted better by the one-dimensional Heisenberg model than the linear Ising model or a singlet-triplet model. The Curie-Weiss constant and the exchange interaction energy along the chain are estimated to be -6.0°K and -5.0°K, respectively. The linewidth of the ESR absorption spectra increases rapidly as decreasing temperature below 6.5°K.