Optical characterization of isothermal spin state switching in an Fe(II) spin crossover molecular and polymer ferroelectric bilayer

Abstract

Using optical characterization, it is evident that the spin state of the spin crossover molecular complex [Fe{H2B(pz)2}2(bipy)] (pz = tris (pyrazol-1-1y)-borohydride, bipy = 2,2’-bipyridine) depends on the electric polarization of an adjacent polymer ferroelectric polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) thin film. The role of the ferroelectric polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) thin film is significant but complex. The UV-Vis spectroscopy reveals that room temperature switching of the electronic structure of [Fe{H2B(pz)2}2(bipy)] molecules in bilayers of PVDF-HFP/[Fe{H2B(pz)2}2(bipy)] occurs as a function of ferroelectric polarization. The retention of voltage-controlled nonvolatile changes to the electronic structure in bilayers of PVDF-HFP/[Fe{H2B(pz)2}2(bipy)] strongly depends on the thickness of the PVDF-HFP layer. The PVDF-HFP/[Fe{H2B(pz)2}2(bipy)] interface may affect PVDF-HFP ferroelectric polarization retention in the thin film limit.

Direct observation of the magnetic anisotropy of an Fe(II) spin crossover molecular thin film

“…Following previous methods [6][7][8][9][10], a [Fe(H 2 B(pz) 2 ) 2 (bipy)] thin film, measured to be 65 nm thick by a Bruker DektakXT profilometer, was thermally evaporated under high vacuum (3.8 × 10 −7 Torr) onto a P/B-doped Si substrate with a native oxide at the surface. The molecular integrity is preserved during this process, as confirmed by the previously published x-ray diffraction data [27]. Field and temperature dependent XMCD measurements were performed at Argonne National Laboratory's Advanced Photon Source beamline 4-ID-C with a beam diameter of 1 mm in total electron yield (TEY) mode [28].…”