EPR Spectra of Multispin Systems. Application to Poly-m-p-Aniline

In this communication we present NiceMagnetic, software for simulations and analysis of EPR spectrum and SQUID measurements. Systems of arbitrary number N of spin-only magnetic moments (S ≤ 0 and L = 0) were considered within the lines of the Heisenberg and Zeeman Hamiltonians. Effective algorithms used for the computations are discussed. This includes modified secant method adapted to calculate resonance fields with demanded precision. Finally, application of NiceMagnetic to experimental SQUID magnetization and EPR spectra of poly-m-p-aniline, one of recently synthesized high spin polymers containing unpaired electrons will be presented. As a result, exchange integral between electron and nitrogen nuclei spins (ligand hyperfine interaction) J = 6.3 × 10$\text{}^{-4}$ cm$\text{}^{-1}$ was estimated.