Magnetic chirality controlled by the interlayer exchange interaction

Chiral magnetism, wherein there is a preferred sense of rotation of the magnetization, has become a key aspect for future spintronic applications. It determines the chiral nature of magnetic textures, such as skyrmions, domain walls or spin spirals, and a specific magnetic chirality is often required for spintronic applications. Current research focuses on identifying and controlling the interactions that define the magnetic chirality. The influence of the interfacial Dzyaloshinskii-Moriya interaction (iDMI) and, recently, the dipolar interactions have previously been reported. Here, we experimentally demonstrate that an indirect interlayer exchange interaction can be used as an additional tool to effectively manipulate the magnetic chirality. We image the chirality of magnetic domain walls in a coupled bilayer system using scanning electron microscopy with polarization analysis (SEMPA). Upon increasing the interlayer exchange coupling, we induce a transition of the magnetic chirality from clockwise rotating N\'eel walls to degenerate Bloch-N\'eel domain walls and we confirm our findings with micromagnetic simulations. In multi-layered systems relevant for skyrmion research a uniform magnetic chirality across the magnetic layers is often desired. Additional simulations show that this can be achieved for reduced iDMI values when exploiting the interlayer exchange interaction. This work opens up new ways to control and tailor the magnetic chirality by the interlayer exchange interaction.Comment: Ms was off by a factor

Time-resolved scanning electron microscopy with polarization analysis

We demonstrate the feasibility of investigating periodically driven magnetization dynamics in a scanning electron microscope with polarizationanalysis based on spin-polarized low-energy electron diffraction. With the present setup, analyzing the time structure of the scattering events, we obtain a temporal resolution of 700 ps, which is demonstrated by means of imaging the field-driven 100 MHz gyration of the vortex in a soft-magnetic FeCoSiB square. Owing to the efficient intrinsic timing scheme, high-quality movies, giving two components of the magnetization simultaneously, can be recorded on the time scale of hours

Magnetic Chirality Controlled by the Interlayer Exchange Interaction

Chiral magnetism, wherein there is a preferred sense of rotation of the magnetization, determines the chiral nature of magnetic textures such as skyrmions, domain walls, or spin spirals. Current research focuses on identifying and controlling the interactions that define the magnetic chirality in thin film multilayers. The influence of the interfacial Dzyaloshinskii-Moriya interaction (IDMI) and, recently, the dipolar interactions have been reported. Here, we experimentally demonstrate that an indirect interlayer exchange interaction can be used as an additional tool to effectively manipulate the magnetic chirality. We image the chirality of magnetic domain walls in a coupled bilayer system using scanning electron microscopy with polarization analysis. Upon increasing the interlayer exchange coupling, we induce a transition of the magnetic chirality from clockwise rotating Néel walls to degenerate Bloch-Néel domain walls and we confirm our findings with micromagnetic simulations. In multilayered systems relevant for skyrmion research, a uniform magnetic chirality across the magnetic layers is often desired. Additional simulations show that this can be achieved for reduced IDMI values (up to 30%) when exploiting the interlayer exchange interaction. This work opens up new ways to control and tailor the magnetic chirality by the interlayer exchange interaction

Quenching of the Resonant Magnetic Scattering by Ultra-Short Free-Electron Laser Pulses

With the advent of free-electron lasers (FELs), new opportunities haveemerged for studying dynamics in matter on ultra-fast time and ultra-shortlength scales simultaneously. As one of the forefront topics within contemporaryresearch on magnetism, studies of ultrafast laser-induced magnetizationdynamics [1] have benefited from these recent developments – revealinga nanoscale spatial response in a domain system coupled to the demagnetizationprocess [2] or transfer of angular momentum between two magneticcompounds in an inhomogeneous magnetic alloy [3]. Such studies of magnetizationdynamics rely on achieving magnetic scattering contrast through theX-ray magnetic circular dichroism (XMCD) effect by tuning the incidentphoton energy resonantly to one of the dichroic M or L absorption edges ofthe magnetic element. However, at extreme FEL fluences, a quenching ofthe resonant magnetic scattering signal was recently observed [4], indicatingthat the FEL radiation does not only act as a probe but also strongly interactswith the sample, effectively altering it already on a time scale shorter thanthe pulse duration of 70 fs. Here, we report on resonant magnetic small-angleX-ray scattering (mSAXS) experiments at the cobalt M3-edge, performed onCo/Pt multilayers with perpendicular magnetic anisotropy showing 100-nmscale magnetic domain patterns, with the purpose of investigating the FELfluence dependence of the resonant magnetic scattering signal. Our results(Figure 1) show a significant reduction (quenching) of the magnetic scatteringstrength with increasing FEL fluence. The intra-pulse quenchingeffect already sets in at much lower fluences than previously expected,revealing the violation of the credo ‘diffract before destruct’ already forthe low fluence regime where the sample is not destroyed by a single-pulseirradiation

Quenching of the Resonant Magnetic Scattering by Ultra-Short Free-Electron Laser Light Pulses

The new free-electron laser (FEL) sources provide radiation with unprecedentedparameters in terms of ultrashort pulse length, high photonflux, and coherence. These properties make FELs ideal tools forstudying ultrafast dynamics in matter on a previously inaccessiblelevel. Yet, FELs do not only probe matter, but can also drive it inhighly excited states which are otherwise inaccessible.Here, we report on a resonant magnetic scattering experiment, wherethe focussed FEL light pulses probe the magnetic domain system of athin magnetic film. Both, single and double FEL pulses at differentfluences are used to follow the quenching of the resonant scatteringefficiency