Antiferromagnetic spin-1/2 chains in (NO)Cu(NO3)3: A microscopic study

We report on the microscopic model of the recently synthesized one-dimensional quantum magnet (NO)Cu(NO3)(3). Applying density-functional-theory band-structure calculations, we obtain a leading antiferromagnetic exchange coupling J similar or equal to 200 K, which runs via NO3 groups forming spin chains along the b direction. Much weaker couplings J' similar or equal to 2 K link the chains into layers in a nonfrustrated manner. Our calculations do not support the earlier conjecture on an anisotropic frustrated square lattice physics in (NO)Cu(NO3)(3). In contrast, the model of uniform spin chains leads to a remarkably good fit of the experimental magnetic susceptibility data, although the low-temperature features of the intrinsic magnetic susceptibility measured by electron spin resonance might call for extension of the model. We outline possible experiments to observe the suggested long-range magnetic ordering in (NO)Cu(NO3)(3) and briefly compare this compound to other spin-1/2 uniform chain systems.