磁性材料、有機分子與二維材料界面形成研究

Interfacial structures formation of 2D and magnetic materials, novel properties of atomic layered films, and organic semiconductor/magnetic heterostructures have been investigated under the support from this project. The main scientific outputs of this project are as follows. (1) Stripe-shaped Co is fabricated by RF sputtering on graphene/Cu substrate and shows a strong shape anisotropy. The coercive force shows an easy axis along the stripe of the substrate. By applying an electric field, the response of the variance of coercive force depends on both the electric potential and the orientation of easy axis. (2) A new finding is demonstrated wherein a phase transition of a superparamagnetic phase can be induced by controlling the thickness of ultrathin ferromagnetic layers. An overstrained film transforming into clusters (OFTC) model based on the new finding and our experimental evidence is proposed for modeling this phenomenon. From the energetic point of view of the OFTC model, we propose a limited distortion mechanism that can be useful in determining the critical thickness for the phase transition. A method for producing superparamagnetic films by taking advantage of the accumulation of strain and relaxation is reported. (3) We report on a novel method using rubrene combined with Kerr microscopy that enables quantitative and direct measurements of magnetic defect density. Experimental evidence shows that coercive force can be reduced by controlling the magnetic defect density by introducing small amounts of rubrene into the films. Direct quantitative measurements of magnetic defects show both a one-dimensional bowing of domain walls and strong defect–domain wall interactions in the films. Based on these findings, we propose a viable strategy for reducing the coercive force of Co/Si(100) by controlling the magnetic defect density and this new information promises to be valuable for future applications of spintronics devices. We have achieved the goal of this project as revealed in the proposal. We have published parts of the results in SCI journals. We appreciate the supports from Ministry of Science and Technology of Taiwan, ROC.