arXiv subjects

D. Pohl

Publications and source records attributed to D. Pohl.

4 recordsLinked to original sources

arXiv2025

Field-induced condensation of $\pi$ to 2$\pi$ soliton lattices in chiral magnets

Chiral soliton lattices (CSLs) are nontrivial spin textures that emerge from the competition between Dzyaloshinskii-Moriya interaction, anisotropy, and magnetic fields. While well established in monoaxial helimagnets, their role in materials with anisotropic, direction-dependent chirality remains poorly understood. Here, we report the direct observation of a tunable transition from $\pi$ to 2$\pi$ soliton lattices in the non-centrosymmetric Heusler compound Mn1.4PtSn. Using Lorentz transmission electron microscopy, resonant elastic X-ray scattering, and micromagnetic simulations, we identify a $\pi$-CSL as the magnetic ground state, in contrast to the expected helical phase, which evolves into a classical 2$\pi$-CSL under increasing out-of-plane magnetic fields. This transition is governed by a delicate interplay between uniaxial magnetocrystalline anisotropy and magnetostatic interactions, as captured by a double sine-Gordon model. Our analysis not only reveals the microscopic mechanisms stabilizing these soliton lattices but also demonstrates their general relevance to materials with D2d, S4, Cnv, or Cn symmetries. The results establish a broadly applicable framework for understanding magnetic phase diagrams in chiral systems, with implications for soliton-based spintronic devices and topological transport phenomena.

cond-mat.mtrl-sci↗

arXiv2025

Microscopic Observation of Non-Ergodic States in Two-Dimensional Non-Topological Bubble Lattices

Disordered 2D lattices, including hexatic and various glassy states, are observed in a wide range of 2D systems including colloidal nanoparticle assemblies and fluxon lattices. Their disordered nature determines the stability and mobility of these systems, as well as their response to the external stimuli. Here we report on the controlled creation and characterization of a disordered 2D lattice of non-topological magnetic bubbles in the non-centrosymmetric ferrimagnetic alloy Mn$_{1.4}$PtSn. By analyzing the type and frequency of fundamental lattice defects, such as dislocations, the orientational correlation, as well as the induced motion of the lattice in an external field, a non-ergodic glassy state, stabilized by directional application of an external field, is revealed.

cond-mat.mtrl-sci↗

arXiv2021

Atomic Layer Deposition of Yttrium Iron Garnet Thin Films for 3D Magnetic Structures

A wide variety of new phenomena such as novel magnetization configurations have been predicted to occur in three dimensional magnetic nanostructures. However, the fabrication of such structures is often challenging due to the specific shapes required, such as magnetic tubes and spirals. Furthermore, the materials currently used to assemble these structures are predominantly magnetic metals that do not allow to study the magnetic response of the system separately from the electronic one. In the field of spintronics, the prototypical material used for such experiments is the ferrimagnetic insulator yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$, YIG). YIG is one of the best materials especially for magnonic studies due to its low Gilbert damping. Here, we report the first successful fabrication of YIG thin films via atomic layer deposition. To that end we utilize a supercycle approach based on the combination of sub-nanometer thin layers of the binary systems Fe$_2$O$_3$ and Y$_2$O$_3$ in the correct atomic ratio on Y$_3$Al$_5$O$_{12}$ substrates with a subsequent annealing step. Our process is robust against typical growth-related deviations, ensuring a good reproducibility. The ALD-YIG thin films exhibit a good crystalline quality as well as magnetic properties comparable to other deposition techniques. One of the outstanding characteristics of atomic layer deposition is its ability to conformally coat arbitrarily-shaped substrates. ALD hence is the ideal deposition technique to grant an extensive freedom in choosing the shape of the magnetic system. The atomic layer deposition of YIG enables the fabrication of novel three dimensional magnetic nanostructures, which in turn can be utilized for experimentally investigating the phenomena predicted in those structures.

cond-mat.mtrl-sci↗

arXiv2018

Spectral field mapping in plasmonic nanostructures with nanometer resolution

Plasmonic nanostructures and devices are rapidly transforming light manipulation technology by allowing to modify and enhance optical fields on sub-wavelength scales. Advances in this field rely heavily on the development of new characterization methods for the fundamental nanoscale interactions. However, the direct and quantitative mapping of transient electric and magnetic fields characterizing the plasmonic coupling has been proven elusive to date. Here we demonstrate how to directly measure the inelastic momentum transfer of surface plasmon modes via the energy-loss filtered deflection of a focused electron beam in a transmission electron microscope. By scanning the beam over the sample we obtain a spatially and spectrally resolved deflection map and we further show how this deflection is related quantitatively to the spectral component of the induced electric and magnetic fields pertaining to the mode. In some regards this technique is an extension to the established differential phase contrast into the dynamic regime.

physics.optics↗