Linear Ising Models and the Antiferromagnetic Behavior of Certain Crystalline Organic Free Radicals

Abstract

Linear Ising models including molecular fields and impurities are employed to interpret the susceptibility and specific heat data of picryl amino carbazyl (PAC), 1,3‐bisdiphenylene 2‐phenyl allyl (BDPA), and Wurster's blue perchlorate (WB). Data taken below 1°K on the linewidth and susceptibility of diphenyl picryl hydrazyl (DPPH) and BDPA is presented. A possible criterion is suggested for distinguishing whether impurities or dislocations are responsible for a low‐temperature susceptibility rise in an antiferromagnetic system. Expressions determining the long‐range order and the correlations between the spins are found.