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Kagome lattices have garnered substantial interest because their band structure consists of topological flat bands and Dirac cones. The RMn6Sn6 (R = rare earth) compounds are particularly interesting because of the existence of the large intrinsic anomalous Hall effect (AHE), which originates from the gapped Dirac cones near the Fermi level. This makes RMn6Sn6 an outstanding candidate for realizing the high-temperature quantum AHE. The growth of RMn6Sn6 thin films is beneficial for both fundamental research and potential applications. However, most of the studies on RMn6Sn6 have focused on bulk crystals, and the synthesis of RMn6Sn6 thin films has not been reported so far. Here, we report the atomic layer molecular beam epitaxy growth, structural and magnetic characterizations, and transport properties of ErMn6Sn6 and TbMn6Sn6 thin films. It is especially noteworthy that TbMn6Sn6 thin films have out-of-plane magnetic anisotropy, which is important for realizing the quantum AHE. Our work paves the avenue toward the control of the AHE using devices patterned from RMn6Sn6 thin films. [ABSTRACT FROM AUTHOR]

The Kagome antiferromagnet Mn 3 Sn has garnered much attention due to the presence of exciting properties such as anomalous Hall and Nernst effects. This paper discusses the synthesis of crystalline Mn 3 Sn thin films, prepared on Al 2 O 3 (0001) substrates at 453 ± 5 ° C using molecular beam epitaxy. The growth is monitored in situ using reflection high energy electron diffraction and measured ex situ using x-ray diffraction, Rutherford back-scattering, and cross-sectional scanning transmission electron microscopy. Our analysis shows the in-plane lattice constants of a 1 , M = 4.117 ± 0.027 Å and a 2 , M = 4.943 ± 0.033 Å, which is a very unexpected result when compared to the bulk a -plane Mn 3 Sn. This indicates a strain in the film and makes it challenging to provide a straightforward explanation. In an effort to explain our results, we discuss two possible orientation relationships between the Mn 3 Sn films and the sapphire substrates. Samples prepared under these conditions appear to have smooth surfaces locally, but overall the film has a 3D island morphology. First-principles calculations provide atomic models of the Mn 3 Sn (11 2 ¯ 0) lattice on Al 2 O 3 (0001) high symmetry sites, indicating that the L3-R90 ° is the most stable configuration. A detailed discussion of the experimental data and theoretical results, as well as strain effects, is provided. [ABSTRACT FROM AUTHOR]

Bi2Te3 is a thermoelectric material with high thermoelectric conversion efficiency near room temperature. The control of its components is an effective method to improve the thermoelectric properties of Bi–Te based materials. In this paper, seven-layer Bi–Te thin films with Te content ranging from 36.29% to 77.29% were deposited on non-rotating glass substrates by co-sputtering and the samples were rapidly thermally annealed in a nitrogen atmosphere. The films were characterized by x-ray diffraction, scanning electron microscopy, and Hall effect measurement methods, and the effects of the components on the film morphology and thermoelectric properties were investigated. The results showed that the films were composed of mainly Bi2Te3 after annealing. As the Te element content increased, the grain size in the film surface first increased and then decreased, the layers between the interfaces became less obvious, and the number of voids decreased. Subsequently, thin films with Te content between 60% and 75% were deposited on a rotating substrate; the thermoelectric properties were relatively high and stable after annealing. A film with Te content of 69.29% had a good crystallization quality and large grain size with a maximum power factor of 8.17 µW/(K2 cm) after annealing at 350 °C for 17 min. [ABSTRACT FROM AUTHOR]

Electrical switching of topological antiferromagnetic states in Mn3Sn thin films has been a subject of active investigation. However, dependences of switching behaviors on the film thickness, external field, and crystal orientation remain to be fully explored, which motivate the present study. In this work, (11 2 ̄ 0) -orientated Mn3Sn thin films are fabricated on sapphire substrates, in which a large anomalous Hall effect over a wide temperature range (270–400 K) can be identified. The current-induced spin–orbit torques (SOTs) are utilized to electrically manipulate the topological antiferromagnetic states in Mn3Sn/Pt bilayers. The robust SOT switching can be realized in Mn3Sn films with thicknesses up to 100 nm and with in-plane fields up to 1200 mT. Furthermore, SOT switching behaviors that are independent of the choice of crystal orientations are clearly revealed. Our results could be useful for implementing Mn3Sn films for efficient and stable antiferromagnetic spintronics. [ABSTRACT FROM AUTHOR]

In the paper [Fang et al., J. Vac. Sci. Technol. B 39, 052208 (2021)], structure and transparent conductive properties of ZnO/Ag/graphene trilayer films with different thicknesses of the Ag layer were investigated. It was found that a continuous Ag layer could be formed at a layer thickness of 10.5 nm, and thus the ZnO/Ag (10.5 nm)/graphene trilayer film could achieve better transparent conductive properties. However, unfortunately, the data of carrier concentration and mobility obtained by the Hall effect for single-layer Ag and ZnO films as well as ZnO/Ag (10.5 nm)/graphene trilayer films have some clear errors that need to be addressed. The authors may consider correcting these errors, perhaps in an erratum. [ABSTRACT FROM AUTHOR]

We report the implementation of a dilution refrigerator-based scanning microwave impedance microscope with a base temperature of ∼100 mK. The vibration noise of our apparatus with tuning-fork feedback control is as low as 1 nm. Using this setup, we have demonstrated the imaging of quantum anomalous Hall states in magnetically (Cr and V) doped (Bi, Sb)2Te3 thin films grown on mica substrates. Both the conductive edge modes and topological phase transitions near the coercive fields of Cr- and V-doped layers are visualized in the field-dependent results. Our study establishes the experimental platform for investigating nanoscale quantum phenomena at ultralow temperatures. [ABSTRACT FROM AUTHOR]

EuTiO3 (ETO) is a unique magnetic semiconductor with a large localized magnetic moment of Eu2+ (4f7). By the doping of high-mobility electrons in the Ti 3d conduction band, peculiar magnetotransport properties such as the unconventional anomalous Hall effect (AHE) due to Berry curvature in momentum space, as well as the Shubnikov–de Haas oscillations of spin polarized electrons, have been observed. In this study, we have examined the physical properties of high quality ETO films with La3+ (4f0) or Gd3+ (4f7) donors (ELTO or EGTO) grown on nearly lattice matched SrTiO3 substrates with a gas source molecular beam epitaxy. We find that the anti-ferromagnetic ordering of ELTO is destabilized by the vacancy of the magnetic moment on the La-site for ELTO. The maximum electron mobility for ELTO (<3200 cm2 V−1 s−1) is larger than that of EGTO (<1500 cm2 V−1 s−1), keeping the metallic state at very diluted doping. The AHE changes its sign with shifting the Fermi level position across the Weyl nodes, as seen previously for compressively strained ELTO films, but the critical electron density is much lower, which can be explained by the absence of additional crystal-field splitting in the lattice matched system. These unveiled transport properties provide deeper understanding of the transport phenomena related to the topology of the band structure in high-mobility, magnetic oxide semiconductors. [ABSTRACT FROM AUTHOR]

Hall transport and non-collinear magnetoresistance (NCMR) are studied for a chiral antiferromagnet (AFM) with the filled β-Mn-type structure. Magnetic and transport properties of epitaxial thin films of Co2−xPdxMo3N revealed that, in addition to a canted antiferromagnetic behavior above room temperature, thin films with x = 1.01∼1.38 exhibited a transition to a spin spiral state with a higher magnetic moment below TSR of around 50 K, which was assigned to a spin reorientation transition. The low-temperature phase shows both large anomalous Hall effect (AHE) and topological Hall effect (THE). Upon the transition to the canted AFM phase existing up to room temperature, the large AHE still persists with vanishing THE. The behavior of the Hall transport properties coupled with NCMR signals in the current-perpendicular-to-the plane configuration shows the formation of topological spin textures with locally antiferromagnetic order. The present results open the way for the study of topological antiferromagnetic spin textures, manipulation of their properties, and for future spintronic applications. [ABSTRACT FROM AUTHOR]

Bi 2 Se 3 is a widely studied 3D topological insulator having potential applications in optics, electronics, and spintronics. When the thickness of these films decreases to less than approximately 6 nm, the top and bottom surface states couple, resulting in the opening of a small gap at the Dirac point. In the 2D limit, Bi 2 Se 3 may exhibit quantum spin Hall states. However, growing coalesced ultrathin Bi 2 Se 3 films with a controllable thickness and typical triangular domain morphology in the few nanometer range is challenging. Here, we explore the growth of Bi 2 Se 3 films having thicknesses down to 4 nm on sapphire substrates using molecular beam epitaxy that were then characterized with Hall measurements, atomic force microscopy, and Raman imaging. We find that substrate pretreatment—growing and decomposing a few layers of B i 2 S e 3 before the actual deposition—is critical to obtaining a completely coalesced film. In addition, higher growth rates and lower substrate temperatures led to improvement in surface roughness, in contrast to what is observed for conventional epitaxy. Overall, coalesced ultrathin Bi 2 Se 3 films with lower surface roughness enable thickness-dependent studies across the transition from a 3D-topological insulator to one with gapped surface states in the 2D regime. [ABSTRACT FROM AUTHOR]

We have experimentally demonstrated a phase change control of Hall effects in ferromagnetic MnBi thin films at room temperature. Two distinct ferromagnetic phases, i.e., a low-temperature phase and a quenched high-temperature phase, were obtained by slow-cooling or quenching the sputtered MnBi films. The measurement of Hall effects showed that the anomalous Hall resistivity has different coercivity and remanence between the two phases. By optimizing the Mn/Bi ratio, it is even possible to repeatedly switch the sign of Hall resistivity, which could be utilized as a concept of phase-change memory based on ferromagnetic transport. [ABSTRACT FROM AUTHOR]

CdO has drawn much recent interest as a high-room-temperature-mobility oxide semiconductor with exciting potential for mid-infrared photonics and plasmonics. Wide-range modulation of carrier density in CdO is of interest both for fundamental reasons (to explore transport mechanisms in single samples) and for applications (in tunable photonic devices). Here, we thus apply ion-gel-based electrolyte gating to ultrathin epitaxial CdO(001) films, using transport, x-ray diffraction, and atomic force microscopy to deduce a reversible electrostatic gate response from −4 to +2 V, followed by rapid film degradation at higher gate voltage. Further advancing the mechanistic understanding of electrolyte gating, these observations are explained in terms of low oxygen vacancy diffusivity and high acid etchability in CdO. Most importantly, the 6-V-wide reversible electrostatic gating window is shown to enable ten-fold modulation of the Hall electron density, a striking voltage-induced metal–insulator transition, and 15-fold variation of the electron mobility. Such modulations, which are limited only by unintentional doping levels in ultrathin films, are of exceptional interest for voltage-tunable devices. [ABSTRACT FROM AUTHOR]

Increase in the Néel temperature (TN) of the 10-nm thick Cr2O3(0001) thin films by the lattice strain was experimentally investigated. TN was determined based on the zero-offset anomalous Hall measurements for the Pt/Cr2O3/Pt epitaxial trilayer. The lattice strain was altered by the Pt buffer layer thickness and was evaluated by the lattice parameters. TN was increased from 241.5 to 260.0 K by varying the Pt buffer layer thickness from 0 to 20 nm. For the film without the Pt buffer layer, the apparent critical exponent near TN increased suggesting the distribution of TN due to the inhomogeneous strain. The TN value was weakly correlated with the axial ratio c/a and the lattice volume of the Cr2O3 layer V; TN increases with decreasing c/a or increasing V. The increase in TN by the reduction in c/a (or by increasing V) implies that the exchange coupling between the nearest neighbor Cr3+ spins has the significant role in the strain effect. [ABSTRACT FROM AUTHOR]