Interface-driven spin filtering and diode effects in van der Waals junctions based on magnetic metal–organic frameworks

Modulating the interface between the molecule and electrode is an effective way to enhance the spin-polarized transport properties of molecular junctions. In this study, using first-principles calculations combined with the nonequilibrium Green's function method, we demonstrate that the spin-transport properties of Cr(pyz)₂ (pyz = pyrazine)-based van der Waals junctions can be significantly regulated by the tunneling barrier and dipole between the molecule-electrode interface. Specifically, we find that the charge transfer and redistribution process within Cr(pyz)₂ can give rise to a transition from a semiconductor to a half-metal in the tunneling junction, leading to a notable enhancement of the spin filtering efficiency (SFE). Besides, partial fluorination of Cr(pyz)₂ has also been demonstrated to effectively enhance the electronegativity of the structure, facilitate the formation of dipole moments within the molecule and at the molecule-metal interface, and induce diode-like behavior. Our results highlight the potential of interface-driven spin filtering and diode effects in Cr(pyz)₂-based van der Waals junctions, paving the way for spintronics device design.