Speaker
Description
Despite demonstrating bistability, the absence of long-range magnetic order and poor electrical conductivity in spin-crossover (SCO) materials limit their prospects in spintronics. Here, we report easily processable Fe-based SCO nanostructures specifically [Fe(Htrz)2(trz)]BF4 grown on 2D reduced graphene oxide (rGO). X-ray photoelectron spectroscopy (XPS) reveals a new bonding state and interfacial charge transfer (CT) between rGO and the SCO nanoparticles. This CT promotes long-range magnetic exchange coupling among Fe(II) centers and induces magnetization within the rGO matrix.
The heterostructure exhibits enhanced cooperativity and magnetic ordering, which is manifested in the appearance of magnetic hysteresis loops. While pristine SCO nanostructures are paramagnetic with zero coercivity, the SCO-rGO hybrid displays a giant coercive field of ~3000 Oe. This induced magnetic order is further supported by temperature-dependent Mössbauer spectra analysis, which reveals the proportion of Fe(II) spin states and underscores how the 2D network enhances intermolecular interactions.
We addressed the typically insulating nature of SCO materials (conductance ~10-11 S) by embedding them on the conducting rGO template, which enhances conductance by six orders of magnitude (~10-5 S). This facilitates the detection of bistable spin states through conductance switching. Temperature-dependent transport data (I-V characteristics) demonstrate sharp spin-state transitions near room temperature, with the low-spin (LS) to high-spin (HS) transition resulting in significant conductance drops (up to 136%). Ab initio calculations corroborate these findings, confirming that interfacial charge transfer opens additional super-exchange pathways, thereby strengthening magnetic interactions in the hybrid architecture.