Optically Gated Terahertz-Field-Driven Switching of Antiferromagnetic CuMnAs

We show scalable and complete suppression of the recently reported terahertz-pulse-induced switching between different resistance states of antiferromagnetic CuMnAs thin films by ultrafast gating. The gating functionality is achieved by an optically generated transiently conductive parallel channel in the semiconducting substrate underneath the metallic layer. The photocarrier lifetime determines the timescale of the suppression. As we do not observe a direct impact of the optical pulse on the state of CuMnAs, all observed effects are primarily mediated by the substrate. The sample region of suppressed resistance switching is given by the optical spot size, thereby making our scheme potentially applicable for transient low-power masking of structured areas with feature sizes of about 200 nm and even smaller

Spontaneous anomalous Hall effect arising from an unconventional compensated magnetic phase in a semiconductor

The anomalous Hall effect, commonly observed in metallic magnets, has been established to originate from the time-reversal symmetry breaking by an internal macroscopic magnetization in ferromagnets or by a non-collinear magnetic order. Here we observe a spontaneous anomalous Hall signal in the absence of an external magnetic field in an epitaxial film of MnTe, which is a semiconductor with a collinear antiparallel magnetic ordering of Mn moments and a vanishing net magnetization. The anomalous Hall effect arises from an unconventional phase with strong time-reversal symmetry breaking and alternating spin polarization in real-space crystal structure and momentum-space electronic structure. The anisotropic crystal environment of magnetic Mn atoms due to the non-magnetic Te atoms is essential for establishing the unconventional phase and generating the anomalous Hall effect.Comment: 34 pages, 14 figure

Optically Gated Terahertz-Field-Driven Switching of Antiferromagnetic CuMnAs

We show scalable and complete suppression of the recently reported terahertz-pulse-induced switching between different resistance states of antiferromagnetic CuMnAs thin films by ultrafast gating. The gating functionality is achieved by an optically generated transiently conductive parallel channel in the semiconducting substrate underneath the metallic layer. The photocarrier lifetime determines the timescale of the suppression. As we do not observe a direct impact of the optical pulse on the state of CuMnAs, all observed effects are primarily mediated by the substrate. The sample region of suppressed resistance switching is given by the optical spot size, thereby making our scheme potentially applicable for transient low-power masking of structured areas with feature sizes of about 200 nm and even smaller

Aufgaben und Ergebnisse des Wirkens der Grundorganisationen der FDJ in der elektrotechnischen Industrie der DDR bei der Entwicklung der naturwissenschaftlich-technischen Intelligenz 1971 - 1976

DB Leipzig(101) - Di 1979 B VD 19 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Signatures of the Magnetic Entropy in the Thermopower Signals in Nanoribbons of the Magnetic Weyl Semimetal Co₃Sn₂S₂

Weyl semimetals exhibit interesting electronic properties due to their topological band structure. In particular, large anomalous Hall and anomalous Nernst signals are often reported, which allow for a detailed and quantitative study of subtle features. We pattern single crystals of the magnetic Weyl semimetal Co3Sn2S2 into nanoribbon devices using focused ion beam cutting and optical lithography. This approach enables a very precise study of the galvano- and thermomagnetic transport properties. Indeed, we found interesting features in the temperature dependency of the anomalous Hall and Nernst effects. We present an analysis of the data based on the Mott relation and identify in the Nernst response signatures of magnetic fluctuations enhancing the anomalous Nernst conductivity at the magnetic phase transition

Observation of an unexpected negative magnetoresistance in magnetic Weyl semimetal Co₃Sn₂S₂

Time-reversal symmetry breaking allows for a rich set of magneto-transport properties related to electronic topology. Focusing on the magnetic Weyl semimetal Co3Sn2S2, we prepared micro-ribbons and investigated their transverse and longitudinal transport properties from 100 K to 180 K in magnetic fields μ0H up to 2 T. We establish the presence of a magnetoresistance (MR) up to 1 % with a strong anisotropy depending the projection of H on the easy-axis magnetization, which exceeds all other magnetoresistive effects. Based on detailed phenomenological modeling, we attribute the observed results with unexpected form of anisotropy to magnon MR resulting from magnon-electron coupling. Moreover, a similar angular dependence is also found in the transverse resistivity which we show to originate from the combination of ordinary Hall and anomalous Hall effects. Thus the interplay of magnetic and topological properties governs the magnetotransport features of this magnetic Weyl system

Atomic layer deposition of yttrium iron garnet thin films

Magnetic nanostructures with nontrivial three-dimensional (3D) shapes enable complex magnetization configurations and a wide variety of new phenomena. To date predominantly magnetic metals have been considered for nontrivial 3D nanostructures, although the magnetic and electronic transport responses are intertwined in metals. Here we report the first successful fabrication of the magnetic insulator yttrium iron garnet (Y3Fe5O12, YIG) via atomic layer deposition (ALD) and show that conformal coating of 3D objects is possible. We utilize a supercycle approach based on the combination of subnanometer thin layers of the binary systems Fe2O3 and Y2O3 in the correct atomic ratio with a subsequent annealing step for the fabrication of ALD-YIG films on Y3Al5O12 substrates. Our process is robust against typical growth-related deviations, ensuring a good reproducibility. The ALD-YIG thin films exhibit a high crystalline quality as well as magnetic properties comparable to samples obtained by other deposition techniques. We show that the ALD-YIG thin films are conformal. This enables the fabrication of 3D YIG nanostructures once appropriate nonmagnetic, 3D templates are developed. Such 3D YIG structures build the groundwork for the experimental investigation of curvature-induced changes on pure spin currents and magnon transport effects. © 2022 American Physical Society