The poster addresses spin crossovers. Magnetoelectrics are a class of multiferroic material whereby coupling between the electric and magnetic properties are present. Spin crossover (SCO) metalorganics make for appealing magnetoelectric candidates due to the relative ease at which the arrangement of electrons within the atomic d-orbitals can be changed with external stimuli, such as temperature, pressure, electric field, magnetic field, and optical irradiation. Wherein, changes in metal-ligand bond lengths are strongly correlated with overall change in electronic spin. Coupling between the molecular magnetic properties and the elastic degrees of freedom of the lattice, as well as the charge in these systems yield magnetic/charge bi-stability, and more importantly, a strong spin-lattice component that drives cooperativity via local lattice strains. Thus, spin-lattice coupling allows for rapid propagation of spin switching to adjacent sites when one site begins to undergo a phase change, which allow for large changes in magnetic susceptibility with relatively small perturbations.
In this investigation, a metalorganic Mn3+ SCO complex that undergoes a complete transition from a high spin (HS) S = 2 state to a low spin (LS) S = 1 state below a sharp transition (T1/2 = 51 K; with < 10 K hysteresis), was studied using continuous-wave high-field powder electron paramagnetic resonance (EPR) spectroscopy. Magnetic anisotropy in d-block transition metals is dominated by spin-orbit coupling, which admixes crystal field states, and can be characterized by parameterizing both g and the zero field splitting terms D and E in the effective spin Hamiltonian. In some SCO complexes, it can be too energetically costly to convert all the sites in the lattice. This results in an inhomogeneous mixture of phases below the transition temperature, complicating the characterization of the EPR spectrum. Therefore, with the advantage of studying a complex exhibiting a complete SCO transition around temperatures amenable to study using EPR, the ZFS parameters were obtained for both the LS and HS states.
HILL GROUP EPR 