Novel Materials for Spintronic Devices

Abstract

Spintronic devices are devices which use the spin properties of atoms to store information. Such devices are predicted to be lower power. In this work, two Fe- II spin crossover molecules are analyzed as candidate novel materials for spintronic devices through computational and experimental work. The molecular activation energy for spin crossover molecule [Fe{H2B(pz)2}2(bipy)] in thin film on a ferroelectric substrate is estimated using Monte Carlo simulations of an Ising-like Model to be 88 meV when the substrate is polarized towards the thin film surface and 198 meV when the substrate is polarized away from the thin film surface. Additional Monte Carlo simulations suggests that beyond-nearest neighbor interactions are required for observed spin-state domain formation. The magnetic anisotropy and spectroscopic g factor for [Fe{H2B(pz) 2}2 (bipy)] molecules are characterized using X-ray magnetic circular dichroism measurements; thin films were dominated by magnetocrystalline anisotropy and the spin-orbit coupling energy was found to be 1.47 kJ m-3. Spin and orbital moment anisotropy estimations from the XMCD measurement were 30.9 and 5.04 meV molecule-1, respectively, and the zero-field g factor was estimated to be gz = 2.26. The optical energy gap for [Fe{HB(tz)3}2] is estimated to be 1.93±0.15 eV using UV-Vis spectroscopic measurements and a newly derived Tauc method for large molecules in solvent. Finally, the [Fe{HB(tz)3}2] molecule in thin film form is confirmed to have increased resistance in the high-spin state, with an on-off ratio of 103. These measurements contribute to the development of novel spintronic devices.