Unveiling the role of Fe₃O₄ in polymer spin valve near Verwey transition

The spinterface formed between ferromagnetic (FM) electrode and organic materials is vital for performance optimization in organic spin valve (OSV). Half-metallic Fe₃O₄ with drastic change in structure, conductivity and magnetic property near Verwey transition can serve as an intrinsic spinterface regulator. However, such modulating effect of Fe₃O₄ in OSV has not been comprehensively investigated, especially below the Verwey transition temperature (T_v). Here, we highlight the important role of Fe₃O₄ electrode in reliable-working and controllable Fe₃O₄/P3HT/Co polymer spin valves by investigating the magnetoresistance (MR) above and below T_v. In order to distinguish between different contributions to charge transport and related MR responses, the systematic electronic and magnetic characterizations were carried out in full temperature range. Particularly, the first-order metal-insulator transition in Fe₃O₄ has a dramatic effect on the MR enhancement of polymer spin valves at T_v. Moreover, both the conducting mode transformation and MR line shape modulation could be accomplished across T_v. This research renders unique scenario to multimodal storage by external thermodynamic parameters, and further reveals the importance of spin-dependent interfacial modification in polymer spin valves.