Raman spectroscopy is a valuable tool in various research fields. The technique yields structural information from all kind of samples often without the need for extensive sample preparation. Since the Raman signals are inherently weak and therefore do not allow one to investigate substances in low concentrations, one possible approach is surface-enhanced (resonance) Raman spectroscopy. Here, rough coin metal surfaces enhance the Raman signal by a factor of 10(4)-10(15), depending on the applied method. In this review we discuss recent developments in SERS spectroscopy and their impact on different research fields.
Spin waves offer intriguing novel perspectives for computing and signal processing, since their damping can be lower than the Ohmic losses in conventional CMOS circuits. For controlling the spatial extent and propagation of spin waves on the actual chip, magnetic domain walls show considerable potential as magnonic waveguides. However, low-loss guidance of spin waves with nanoscale wavelengths, in particular around angled tracks, remains to be shown. Here we experimentally demonstrate that such advanced control of propagating spin waves can be obtained using natural features of magnetic order in an interlayer exchange-coupled, anisotropic ferromagnetic bilayer. Using Scanning Transmission X-Ray Microscopy, we image generation of spin waves and their propagation across distances exceeding multiple times the wavelength, in extended planar geometries as well as along one-dimensional domain walls, which can be straight and curved. The observed range of wavelengths is between 1 µm and 150 nm, at corresponding excitation frequencies from 250 MHz to 3 GHz. Our results show routes towards practical implementation of magnonic waveguides employing domain walls in future spin wave logic and computational circuits.
The magnetization reversal process in the ferromagnetic layer of an exchange-biased Co90Fe10(20 nm)/Ir23Mn77(10 nm) film structure, deposited by dc-magnetron sputtering, is imaged by high-resolution Kerr microscopy. Additionally, high-resolution magnetization loops are measured by deriving the magnetization signal from the average image intensity. The magnetization reversal occurs first by magnetization rotation under the development of ripple-like structures. The modulated structures then partially switch, generating complicated multidomain configurations, which finally annihilate by large angle domain wall movement. The amount of magnetization rotation at different field directions is quantified by measuring the transversal magnetization components during reversal. A strong asymmetry, both in domain behavior and magnetization loop, between the forward and recoil branch of the magnetization reversal is found. The magnitude of asymmetry strongly depends on small angle misalignments between the direction of exchange-bias and the external magnetic field. The observed domain behavior is explained by anisotropy dispersion in the ferro- and antiferromagnetic layer. The observed differences for both branches of the hysteresis loop are described in terms of domain nucleation mechanisms due to changes in the antiferromagnetic layer leading to an effectively wider anisotropy distribution.
The Pt magnetization depth profile at a single buried Pt/Co interface was investigated by x-ray resonant magnetic reflectivity measurements. The asymmetry as function of angle of incidence has been measured in the Pt L 3 -near-edge absorption region at two energies. Observed asymmetry ratios in the order of 0.5% are described on the basis of a magnetically modified Parratt algorithm. Excellent agreement between simulations and experiment was achieved for a Pt magnetic moment of 0.21 B at the rough interface followed by an exponential decay of the induced polarization within 1 nm.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.