Spin-Polarised Scanning Tunnelling Microscopy and Relevant Techniques — A Survey of Present Status

Abstract

Spin-polarised STM and related techniques have emerged amid a general background where the advance of materials research is demanding ever more powerful analytical tools. In the field of thin film magnetism, the ability to grow epitaxial metallic films to a high degree of perfection has generated fascinating new topics. For example, there has been considerable research activities in the magnetic behaviour of multilayer structures made of thin metallic layers with a thickness of a few atoms. These multilayers exhibit a number of interesting effects such as oscillations in the interlayer coupling and giant magnetoresistance (MR)1–5. Because of their novel behaviour, these thin films may find their way to potential technological applications: for instance, magnetic-field detection, for which a large MR at small fields is desirable. Epitaxial magnetic films grown on suitable substrates have also led to the study of films with crystallographic structures not commonly found in nature as well as the study of magnetism of reduced dimensions. As an important subject in both fundamental research and data storage applications, the observation of magnetic domain structures is now being performed on an ever-decreasing lateral scale. From the point of view of technological applications, as data recording density increases such that the domain size in magnetic thin film media is shrinking to submicron level, the structures and characterisation of domain boundaries are becoming more important. It is also evident that the ultimate goal of surface magnetic studies would involve establishing the electron spin polarisation and the electronic state of each surface atom with atomic resolution.