Multidimensional Spectromicroscopy of Molecular Magnetism

非技术摘要：交换耦合是电子自旋的基本性质。交换耦合的大小和符号定义了自旋之间相互作用的强度和方向，这对于理解各种磁和自旋电子现象至关重要。但到目前为止，还没有测量到交换耦合的空间依赖性。这个项目使用自制的仪器和先进的计算方法，以前所未有的细节探测磁性原子和分子之间的交换相互作用。这些活动为培训研究人员提供了肥沃的土壤。这项研究的结果被转移到课堂上，为物理和工程专业的本科生讲授量子力学。此外，目标是通过将选定的结果转移到教科书中来增加影响，类似于研究人员之前从扫描隧道显微镜获得的结果。研究结果可能在未来的磁性技术中得到应用。在南加州，本科生作为暑期实习生的培训和与拉美裔中学生的外展活动得到了广泛的承诺。技术摘要：由吸附在固体表面上的磁性原子和分子相互作用形成的量子化自旋系统的哈密顿量产生了依赖于交换相互作用J和磁各向异性(A)的能谱(E)。该项目利用自制的超高真空扫描隧道显微镜(STM)在600MK和高达9特斯拉的磁场下探测四维(E，x，y，z)磁性实体之间的J和A。研究两个自旋实体之间的连续相互作用是通过将磁性分子附着到STM针尖上来检测表面上不同的磁性实体，从孤立的磁性原子或分子(如茂金属、卟啉和酞菁)到纳米级的组装。垂直于表面和平行于表面的不同尖端位置的E谱给出了J和A的空间依赖关系，并通过光谱显微镜对它们进行了可视化。这个项目结合了实验和理论的共同努力，在四个维度上测量和理解自旋-自旋耦合中包含的新信息。被探测系统的明确条件使得实验和理论之间能够进行严格的比较，以便在最基本的水平上有效地理解自旋-自旋耦合。过去，由于无法获得可靠的量化数据，这一努力一直受到阻碍。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical Abstract: The exchange coupling is a fundamental property of the electron spins. The magnitude and sign of exchange coupling define the strength and direction of the interaction between spins, essential for the understanding of a variety of magnetic and spintronic phenomena. But so far the spatial dependence of exchange coupling has not been measured. This project uses homemade instruments and advanced calculations to probe in unprecedented details the exchange interactions among magnetic atoms and molecules. These activities provide fertile grounds for the training of researchers. Results from this research are transferred into the classroom for the teaching of quantum mechanics to undergraduate students in physics and engineering. In addition, the goal is to increase impact by transfer of selected results to the textbooks, similarly to previous results from the scanning tunneling microscope obtained by the investigators. Results may be applied in future magnetic technologies. Extensive commitments are made in the training of undergraduate students as summer interns and outreaching activities with the Hispanic middle school students in Southern California.Technical Abstract: The Hamiltonian for a quantized spin system formed by interacting magnetic atoms and molecules adsorbed on a solid surface yields an energy spectrum (E) that depends on the exchange interaction J and the magnetic anisotropy (A). This project probes J and A between magnetic entities in four dimensions (E,x,y,z) with a homemade ultrahigh vacuum scanning tunneling microscope (STM) at 600 mK and up to 9 Tesla magnetic field. The study of the continuous interactions between two spin entities is achieved by attaching a magnetic molecule to the STM tip to sense different magnetic entities on the surface, from an isolated magnetic atom or molecule (such as metallocenes, porphyrins, and phthalocyanines) to nanoscale assemblies. The E-spectra at different tip locations, perpendicular and parallel to the surface, give the spatial dependence of J and A, and their visualization through spectromicroscopy. This project combines a joint experimental and theoretical effort to measure and understand the new information contained in the spin-spin coupling in four dimensions. The well-defined conditions of the probed systems enable rigorous comparison between experiment and theory to effectively understand spin-spin coupling at the most fundamental level. This effort has been impeded in the past due to unavailability of reliable, quantitative data.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.