Generation and Propagation of Ultrafast Terahertz Magnons in Atomically Architectured Nanomagnets.

Utilizing ultrafast terahertz (THz) magnons, the quanta of collective magnetic excitations, as carriers may provide a promising alternative to overcome the problems associated with electrical losses in nanoelectronic devices and circuits. However, efficient excitation of propagating coherent THz magnons in magnonic nanowaveguides is an essential requirement for the development of such devices. Here, by growing ultrathin ferromagnetic nanostructures on a reconstructed surface, we create well-ordered periodic magnetic nanostripes.

Giant Spin-Orbit Induced Magnon Nonreciprocity in Ultrathin Ferromagnets.

The propagation characteristics of fermionic and bosonic quasiparticles determine the fundamental transport properties of solids and are of great technological relevance for designing logic devices. In particular, nonreciprocity, which describes that a quasiparticle flows preferably along a certain direction of a symmetry path, is an essential requirement to realize logic architectures, e.g.

Direct Probing of a Large Spin-Orbit Coupling in the FeSe Superconducting Monolayer on STO.

Spin-orbit coupling (SOC) is a fundamental physical interaction, which describes how the electrons' spin couples to their orbital motion. It is the source of a vast variety of fascinating phenomena in nanostructures. Although in most theoretical descriptions of high-temperature superconductivity SOC has been neglected, including this interaction can, in principle, revise the microscopic picture.

Magnonic crystals: towards terahertz frequencies.

This topical review presents an overview of the recent experimental and theoretical attempts on designing magnonic crystals for operation at different frequencies. The focus is put on the microscopic physical mechanisms involved in the formation of the magnonic band structure, allowed as well as forbidden magnon states in various systems, including ultrathin films, multilayers and artificial magnetic structures. The essential criteria for the formation of magnonic bandgaps in different frequency regimes are explained in connection with the magnon dynamics in such structures.

Spin waves in disordered materials.

We present an efficient methodology to study spin waves in disordered materials. The approach is based on a Heisenberg model and enables calculations of magnon properties in spin systems with disorder of an arbitrary kind and concentration of impurities. Disorder effects are taken into account within two complementary approaches.

Probing of the interfacial Heisenberg and Dzyaloshinskii-Moriya exchange interaction by magnon spectroscopy.

This Topical Review presents an overview of the recent experimental results on the quantitative determination of the magnetic exchange parameters in ultrathin magnetic films and multilayers grown on different substrates. The experimental approaches for probing both the symmetric Heisenberg and the antisymmetric Dzyaloshinskii-Moriya exchange interaction in ultrathin magnetic films and at interfaces are discussed in detail. It is explained how the experimental spectrum of magnetic excitations can be used to quantify the strength of these interactions.