Room-Temperature Long-Range Ferromagnetic Order in a Confined Molecular Monolayer

Pursuing new ferromagnetic systems could bring about research breakthroughs for magnetism. Currently, studies of magnetic ordering are expanding from interatomic to intermolecular exchange interactions to produce ferromagnets in inorganic/organic crystals. To date, the crystalline framework used for stabilizing parallel spin alignment via an ordered lattice seems to be indispensable to ferromagnetism. In our case, we demonstrated room-temperature long-range ferromagnetic order in two-dimensional confined cobaltocene (Co(Cp)2) molecular monolayers. In a confined van der Waals (vdW) interlayer space, spontaneous uniform spin orientation of Co(Cp)2 can be settled. Ferromagnetic coupling is established by an intermolecular vibronic superexchange interaction, a new long-distance exchange interaction in a cooperative dynamic Jahn-Teller (J-T) Co(Cp)2 monolayer. As expected, the confined Co(Cp)2 monolayers exhibit a high ferromagnetic transition temperature (above room temperature) with a saturation magnetization up to 4 emu.g-1.