MAGNETIC AND THERMAL STUDIES OF DI-P-ANISYLNITROSYL

The static magnetic susceptibility from 1.4 to 300°K and the zero-field specific heat from 1.0 to 15°K of the stable aromatic free-radical di-p-anisylnitrosyl have been measured on powder samples. The data are shown to be consistent with nearest-neighbor antiferromagnetic Heisenberg exchange (S=12) of a quadratic layer lattice. The nearest-neighbor exchange integral is estimated to be 2.4°K. Both a discontinuity in dχdT and a slight indication of an anomaly in the specific heat at 2.7°K indicate a possible antiferromagnetic transition at that temperature. The susceptibility exhibits a Curie-Weiss law χ-1=2.86(T+3.4K) mole/emu at high temperatures and a broad maximum at about 4.1°K. The specific heat is resolved into a lattice T3 contribution characterized by a Debye temperature of 83.5±2°K, and a magnetic contribution characterized by an entropy per mole of 98% of the expected Rln2. The magnetic specific heat exhibits a broad maximum at a temperature of about 3.1°K. © 1969 The American Physical Society.