Optical investigations of the magnetic properties of iron nanostructures grown on tungsten(110)

Abstract

The structural and magnetic properties of ultra-thin Fe films and Fe nanostripes grown on vicinal W(110) are studied using Reflectance Anisotropy Spectroscopy (RAS), and the non-linear optic techniques of Second Harmonic Generation (SHG) and Magnetic Second Harmonic Generation (MSHG). Using Au as a capping material, it is possible to transfer the ultra-thin Fe films from the Ultra-high Vacuum (UHV) environment to the ambient laboratory atmosphere without destroying their magnetic properties, thereby allowing both in situ and ex situ investigations to be carried-out. The ex-situ investigations revealed significant MSHG contributions from Au-capped Fe nanostripes just 10 atoms wide (corresponding to a 0.25ML Fe film), thereby demonstrating the extreme magnetic sensitivity of non-linear optic techniques in probing surface magnetism. Measuring the temperature dependence of the MSHG contrast as a function of sample temperature allowed the Curie point of the surface magnetism to be determined, while measuring the M SHG signal as a function of applied field allowed the hysteresis loops of the surface magnetization to be deduced.