Abstract
The quantum Hall effect (QHE) is traditionally considered to be a purely two-dimensional (2D) phenomenon. Recently, however, a three-dimensional (3D) version of the QHE was reported in the ...Dirac semimetal ZrTe
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. It was proposed to arise from a magnetic-field-driven Fermi surface instability, transforming the original 3D electron system into a stack of 2D sheets. Here, we report thermodynamic, spectroscopic, thermoelectric and charge transport measurements on such ZrTe
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samples. The measured properties: magnetization, ultrasound propagation, scanning tunneling spectroscopy, and Raman spectroscopy, show no signatures of a Fermi surface instability, consistent with in-field single crystal X-ray diffraction. Instead, a direct comparison of the experimental data with linear response calculations based on an effective 3D Dirac Hamiltonian suggests that the quasi-quantization of the observed Hall response emerges from the interplay of the intrinsic properties of the ZrTe
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electronic structure and its Dirac-type semi-metallic character.
•Topological Hall effect found in Pt/Co/W multilayers with different signs of anisotropy.•Negative topological Hall contribution due to nucleated isolated skyrmions.•Positive topological Hall ...contribution isolated non-annihilated skyrmions.•Skyrmion numbers of complex domain structures reproduced micromagmetically.
The chirality of non-coplanar magnetic configurations, in magnetic materials with interfacial Dzyaloshinskii–Moriya interaction, gives rise to a local magnetic field generating an extra contribution to the anomalous Hall effect. This contribution, termed topological Hall effect (THE), is studied in three Pt/Co/W multi-layered samples with different effective anisotropy. A particularity of this system, compared to similar systems which show THE, is the existence of magnetically inactive layers at the Co/W interfaces. This implies that the coupling between the layers in this series of samples is mainly magnetostatic. The samples with positive or almost zero effective anisotropy show the same characteristics. These are reproduced by micromagnetic simulations. The sample with negative effective anisotropy shows a qualitatively different behaviour that can be assigned to its radically different domain structure. The values of THE are in the range 0.1–0.25 μΩ cm.
The quantum Hall effect (QHE) is traditionally considered to be a purely two-dimensional (2D) phenomenon. Recently, however, a three-dimensional (3D) version of the QHE was reported in the Dirac ...semimetal ZrTe
. It was proposed to arise from a magnetic-field-driven Fermi surface instability, transforming the original 3D electron system into a stack of 2D sheets. Here, we report thermodynamic, spectroscopic, thermoelectric and charge transport measurements on such ZrTe
samples. The measured properties: magnetization, ultrasound propagation, scanning tunneling spectroscopy, and Raman spectroscopy, show no signatures of a Fermi surface instability, consistent with in-field single crystal X-ray diffraction. Instead, a direct comparison of the experimental data with linear response calculations based on an effective 3D Dirac Hamiltonian suggests that the quasi-quantization of the observed Hall response emerges from the interplay of the intrinsic properties of the ZrTe
electronic structure and its Dirac-type semi-metallic character.
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.
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