The transition from quantum to classical magnetism investigated by scanning tunneling microscopy

气相中单原子的磁性早已为人们所知，并得到了高精度的测量。在另一个极端的长度尺度上，块状磁体的磁性也得到了很好的理解，并已被用于许多技术应用，例如硬盘驱动器中的磁数据存储。通过直接或间接交换作用相互耦合的数量众多的磁性原子的中间体系，是从量子世界过渡到经典世界的桥梁，最近导致了具有新磁性的单分子磁体的令人兴奋的发现。在磁性的量子极限方面，IBM扫描隧道显微镜(STM)小组最近成功地测量了工程原子尺度磁结构的自旋激发，得到了关于它们的基态和激发态的详细信息。为了研究纳米结构中的磁性，汉堡的研究小组在最近几年建立了自旋分辨扫描隧道显微镜的方法：人们可以直接映射由经典的海森堡模型−描述的具有高空间分辨率的自旋结构−。这个项目的目的是通过结合上述两种方法的优点，用扫描隧道显微镜研究量子和经典磁性极限之间的跃迁。

The magnetic properties of single atoms in the gas phase have been known and measured with high precision for a long time. On the other extreme of length scales, the magnetic properties of bulk magnets are also well understood and have been harnessed for many technological applications such as magnetic data storage in hard disk drives. The inter-mediate regime of a countable number of magnetic atoms coupled to each other through direct or indirect exchange interactions bridges the transition from the quantum to the classical world and has recently led to the exciting discovery of single molecule magnets with novel magnetic properties. In the quantum limit of magnetism the IBM scanning tunneling microscopy (STM) group has recently succeeded in measuring spin excitations of engineered atomic-scale magnetic structures which have yielded detailed information about their ground and excited states. The method of spin-resolved STM has been established over the last years by the group in Hamburg for the investigation of magnetism in nanostructures: one can directly map the spin structure −describable by the classical Heisenberg model− with high spatial resolution. The aim of this proposed project is to study the transition between the quantum and the classical limit of magnetism using STM by combining the strengths of the two above-mentioned approaches of spin excitation and local spin-resolved measurements.