Surface-driven magnetism in ultrathin ferromagnetic and antiferromagnetic films

传统材料的极薄（2到10个原子层）薄膜的材料特性通常是非常规的。这可能是因为这些薄膜采用了一种非常规的结构，因为它们是二维的而不是三维的系统，因为表面起着重要的作用，或者因为其他原因。对传统磁性材料（如铁和镍）的超薄膜磁性的研究就是一个很好的例子，其中观察到许多以前未知的磁性现象，其中一些导致在磁性数据存储和检索中的应用。本提案旨在研究超薄磁性薄膜的两个主要观点。首先是继续研究铁薄膜从磁性态到非磁性态的转变。这项工作解决了关于这种转变如何在二维材料中发生的基本问题。第二是学习如何生长反铁磁薄膜，即每一个其他原子的磁矩是相反排列的薄膜。这种状态在块状晶体中是众所周知的，但目前还没有一种简单的方法可以在超薄膜中检测到它。我们建议改进光磁响应技术以实现这些测量，并为这类难以捉摸的材料打开一扇窗。

The materials properties of extremely thin (2 to 10 atom layers) films of conventional materials are often unconventional.  This can be because these films take an unconventional structure, because they act as 2-dimensional rather than 3-dimensional systems, because surfaces play an important role, or because of other reasons.  The investigation of the magnetic properties of ultrathin films of conventional magnetic materials such as iron and nickel is an excellent example, where a number of previously unknown magnetic phenomena have been observed, some of them leading to applications in magnetic data storage and retrieval. This proposal aims to investigate two main ideas in the context of ultrathin magnetic films.  The first is to continue our studies of the transition from the magnetic state to the non-magnetic state in iron films.  This work addresses fundamental questions concerning how this transition occurs in a 2-dimensional material.  The second is to learn how to grow antiferromagnetic films -- i.e. films where the magnetic moment of every other atom is aligned oppositely.  This state is well known in bulk crystals, but at present, there is no simple way to detect it in ultrathin films.  We propose to refine optical magnetic response techniques to allow these measurements, and to open a window on this elusive class of materials.