Magnetic second-harmonic generation from interfaces and nanostructures

Abstract

Magneto-optic techniques provide non-contact and non-destructive characterization of magnetic materials. This includes embedded magnetic nanostructures, which are accessible due to the large penetration depth of optical radiation. The linear magneto-optic Kerr effect is widely used in the growth and characterization of ultra-thin magnetic films and can show monolayer sensitivity. Nonlinear magnetic second-harmonic generation (MSHG) is a more difficult and expensive technique but, uniquely, can measure the surface and interface magnetism of centrosymmetric magnetic films with sub-monolayer sensitivity. MSHG is briefly reviewed and examples from high symmetry interfaces and nanostructures described. Low symmetry structures are more difficult to characterize, however, because of the large number of tensor components that may contribute to the signal. An important class of low symmetry systems exploits vicinal substrates to grow aligned magnetic nanostructures by self-organization. These structures have a high proportion of magnetic step or edge atoms relative to the terrace atoms, and the overall magnetic response is expected to contain significant contributions from these different magnetic regions. It is shown that contributions from these different regions can be identified using normal A c c e p t e d m a n u s c r i p t -2 -incidence (NI) MSHG. This new approach is used to determine hysteresis loops from Au-capped Fe monolayers grown on a vicinal W(110) substrate. Temperature-dependent studies of the MSHG contrast also allow Curie temperatures to be determined. This experimental procedure and phenomenology opens up low symmetry magnetic interfaces and aligned nanostructures to characterization by MSHG.

Adsorption Kinetics of Ultrathin Polymer Films in the Melt Probed by Dielectric Spectroscopy and Second-Harmonic Generation

“…The SHG signal is very sensitive to any breaking of inversion symmetry in materials, induced by e.g. internal electrical or magnetic fields, surfaces, and interfaces. , The symmetry at interfaces can also be broken by molecular adsorption . The particular arrangement of the adsorbed molecules, oriented parallel or perpendicular to the interface, can in itself constitute a source of SHG signal.…”

Probing surface and interface structure using optics

“…• , for Fe nanostripes ten atoms wide (left column) and for 3 ML Fe coverage (right column), grown on vicinal W(110) and capped by 15 nm of Au [125]. The temperature dependence of the magnetic contrast is also plotted.…”

Magnetic properties of the CoO/Fe(001) system with a bottom-up engineered interface

“…In this work, we aim to unveil further details related to the origin of the interface magnetic anisotropy, in particular by focusing on the magnetic properties of the interface itself and on the magnetic nature of the CoO overlayer. The first aspect was investigated by measuring magnetic hysteresis loops through Magnetic Second Harmonic (MSH) generation [11][12][13]. The latter technique is known to be particularly sensitive to magnetic effects associated with surfaces and interfaces, with several examples related in particular to AF/FM interfaces [14,15].…”