Spatial distribution of phases during gradual magnetostructural transitions in copper(ii)–nitroxide based molecular magnets

Abstract

Copper(II)–nitroxide based molecular magnets Cu(hfac)₂L^R exhibit thermally-induced transitions between high- and low-temperature (HT/LT) magnetostructural states. In this work we report the first study on the spatial distribution of HT/LT phases during gradual transitions in these compounds. We explore the possibility of domain formation at intermediate temperatures, which has never been addressed before. For this purpose, we reexamine the available electron paramagnetic resonance (EPR) and X-ray diffraction data, and perform numerical calculations of EPR spectra for different models of exchange-coupled networks. A thorough analysis shows that during gradual transitions, molecular magnets Cu(hfac)₂L^R represent solid solutions of disordered HT and LT phases, and the formation of single-phase domains larger than a few nanometers in size is unlikely.