Integrating Remote Sensing and Geophysics for Exploring Early Nomadic Funerary Architecture in the “Siberian Valley of the Kings”

This article analyses the architecture of the Early Iron Age royal burial mound Tunnug 1 in the “Siberian Valley of the Kings” in Tuva Republic, Russia. This large monument is paramount for the archaeological exploration of the early Scythian period in the Eurasian steppes, but environmental parameters make research on site difficult and require the application of a diversity of methods. We thus integrate WorldView-2 and ALOS-2 remote sensing data, geoelectric resistivity and geomagnetic survey results, photogrammetry-based DEMs, and ortho-photographs, as well as excavation in order to explore different aspects of the funerary architecture of this early nomadic monument. We find that the large royal tomb comprises of a complex internal structure of radial features and chambers, and a rich periphery of funerary and ritual structures. Geomagnetometry proved to be the most effective approach for a detailed evaluation of the funerary architecture in our case. The parallel application of several surveying methods is advisable since dataset comparison is indispensable for providing context

Time resolved magnetization dynamics of ultrathin Fe(001) films: Spin-pumping and two-magnon scattering

The time-resolved magnetic response of ultrathin epitaxial Fe(001) films grown on GaAs(001) and covered by Au, Pd, and Cr capping layers was investigated by time and spatially resolved Kerr effect measurements. The magnetization was excited by an in-plane magnetic field pulse using the transient internal field generated at a Schottky barrier while the wavelength of the excitation (resonant mode) was roughly 4 mu m. Each of the three cap layers affected the spin relaxation in a unique way. Au cap layers resulted in the bulk Gilbert damping of the Fe film. Pd cap layers caused an additional Gilbert damping due to spin-pump or spin-sink effects. Cr cap layers lead to a strong extrinsic damping which can be described by two-magnon scattering. In this case the strength of the extrinsic damping can be controlled by a field induced shift of the spin wave manifold with respect to the excited k vector

Spin dynamics of the antiferromagnetic-to-ferromagnetic phase transition in FeRh on a sub-picosecond time scale

The antiferromagnetic-to-ferromagnetic phase transition in FeRh films induced by heating with a femtosecond laser pulse was investigated using the time-resolved magneto-optical Kerr effect. An initial rise time of the magneto-optical signal of about 500 fs is found as the FeRh is heated through the transition. The data offer a complementary view to previous pump–probe experiments on "simple" ferromagnetic materials and allow a glimpse at the complex interplay between lattice, electron and spin dynamics governing the first-order antiferromagnetic-to-ferromagnetic phase transition of FeRh

Micromagnetic Dissipation, Dispersion, and Mode Conversion in Thin Permalloy Platelets

Micron-sized ferromagnetic Permalloy disks exhibiting an in-plane ferromagnetic vortex structure are excited by a fast rise time perpendicular magnetic field pulse and their modal structure is analyzed. We find azimuthal and axial modes. By a Fourier filtering technique we can separate and analyze the time dependence of individual modes. Analysis of the experimental data demonstrates that the azimuthal modes damp more quickly than the axial modes. We interpret these results as mode conversion from low-frequency azimuthal modes to the fundamental mode which is higher in frequency, i.e., mode-mode coupling in a system with a single Landau-Lifshitz-Gilbert phenomenological damping constant

Pulsed precessional motion on the 'back of an envelope'

In a recent paper (Acremann et al 2000 Science 290 492) the precessional trajectory of the magnetization vector was imaged with spatial resolution as a function of the time elapsed after a magnetic field pulse was applied. The most surprising observations—the reversal of the magnetic excitation upon reflection from the boundary and the spatial non-uniformities of the precessional mode—have remained unaccounted for so far. Here we present a 'back of the envelope' model of the precessional motion that is analytical, free of adjustable parameters, and that reproduces all the essential experimental features, including the behaviour of the dynamical magnetization at boundaries

Magnetic Spatial Non-Uniformities on the Picosecond Timescale

The magnetization of a Co disk with an in-plane flux-closure domain structure was subject to a picosecond magnetic field pulse perpendicular to the plane. Images with sub-micron spatial resolution have been recorded every 10 ps which reveal magnetic non-uniformities of the ferromagnetic resonance (FMR) response. A detailed analysis of the images shows a difference in the FMR frequencies of about 10% as a function of radius. In addition, the magnetization at the edge responds earlier to the applied field pulse. We discuss possible origins of these phenomena

Phase-resolved pulsed precessional motion at a Schottky barrier

The precessional motion of the magnetization is excited by an ultrashort magnetic-field pulse at a Schottky barrier containing a ferromagnetic film. The precessional frequency, measured as a function of a bias field of variable strength and direction by time resolved Kerr microscopy, is accurately reproduced by a model based on the theory of ferromagnetic resonance. The spatially resolved precessional phase reveals a jump related to the chiral character of the exciting magnetic-field pulse

Spin-Wave Eigenmodes of Permalloy Squares with a Closure Domain Structure

Quantized spin-wave eigenmodes in single, 16 nm thick and 0.75 to 4 µm wide square permalloy islands with a fourfold closure domain structure have been investigated by microfocus Brillouin light scattering spectroscopy and time resolved scanning magneto-optical Kerr microscopy. Up to six eigenmodes were detected and classified. The main direction of the spin-wave quantization in the domains was found to be perpendicular to the local static magnetization. An additional less pronounced quantization along the direction parallel to the static magnetization was also observed

Excitations with negative dispersion in a spin vortex

Micron-sized ferromagnetic permalloy disks having an in-plane vortexlike configuration are excited by a fast-rise-time magnetic-field pulse perpendicular to the plane. The excited modes are imaged using time-resolved magneto-optic Kerr microscopy and Fourier transformation. Two types of modes are observed: modes with circular nodes and modes with diametric nodes. The frequency of the modes with circular nodes increases with the number of nodes. In contrast, the frequency of the modes with diametric nodes decreases with the number of nodes. This behavior is explained accurately by an analytical model

High-resolution imaging of fast magnetization dynamics in magnetic nanostructures

By combining magnetic transmission x-ray microscopy with a stroboscopic pump and probe technique using synchrotron radiation we are able to image the magnetization dynamics in micron sized magnetic particles on a sub-100 ps time scale with a lateral spatial resolution down to 21 nm. We report first observations in squared elements indicating locally varying precessional frequencies which are in agreement with micromagnetic simulations. The experiment opens a route towards a high spatiotemporal resolution of spin patterns which is needed to understand the microscopic origin of magnetization reversal of micron sized and nano-sized magnetic particles