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A superconducting interface Interfaces between materials can harbor quantum states that belong to neither of the materials. A classic example is the superconducting interface between two insulating oxides, LaAlO 3 and SrTiO 3 , with a critical temperature of around 200 millikelvin. Liu et al. observed superconductivity at a different interface—formed between KTaO 3 as a substrate and an overlayer of either EuO or LaAlO 3 —at a considerably higher temperature of about 2 kelvin. Transport measurements displayed anisotropy, which may indicate an unusual superconducting state. Science , this issue p. 716

We demonstrate the detection of phase-resolved magnetization dynamics with combinatorial magneto-optic Kerr and Faraday effects. The method uses a continuous-wave laser that is amplitude-modulated at the spin dynamic frequencies and thus allows for coherent tracking of the spin dynamics, akin a “lock-in”-type measurement. In particular, our method, using a single 1550 nm wavelength, probes simultaneously the ferromagnetic (FM) resonance of Y3Fe5O12 (YIG) and Permalloy (Py = Ni80Fe20) in a YIG-Py heterostructure. The fiber-based magneto-optic components also have the advantage of being made into a compact, tabletop or even portable system with yet robust measurement performances. We believe that our method will be found useful in studying hybrid quantum magnonic systems and/or investigating phase-resolved spin dynamics in nanomagnet structures involving both FM insulators and metals.

The ability to control the potential landscape in a medium of interacting particles could lead to intriguing collective behavior and innovative functionalities. Here, we utilize spatially reconfigurable magnetic potentials of a pinwheel artificial spin ice structure to tailor the motion of superconducting vortices. The reconstituted chain structures of the magnetic charges in the artificial pinwheel spin ice and the strong interaction between magnetic charges and superconducting vortices allow significant modification of the transport properties of the underlying superconducting thin film, resulting in a reprogrammable resistance state that enables a reversible and switchable vortex Hall effect. Our results highlight an effective and simple method of using artificial spin ice as an in-situ reconfigurable nanoscale energy landscape to design reprogrammable superconducting electronics, which could also be applied to the in-situ control of properties and functionalities in other magnetic particle systems, such as magnetic skyrmions., Comment: To appear in Nano Letters

One way of making a transition-edge sensor (TES) is by utilizing the proximity effect, in which the $$T_{C}$$ of a superconducting film is reduced with a normal metal film in metallic contact. The $$T_{C}$$ of a bilayer TES can be estimated by solving the Usadel equations with given boundary conditions. The classical boundary conditions of a bilayer include a specific interface resistance being temperature-independent. In this paper, we will introduce a temperature-dependent specific interface resistance. By fitting the measured $$T_{C}$$ data of Ir/Au bilayers from the literature to a $$T_{C}$$ calculation model, we will compare the fit parameters and fit errors with the temperature-dependent specific interface resistance described in this work and with the classical temperature-independent specific interface resistance.

Description, Applying heat to a magnetoelectric antiferromagnet enables an electric field control of magnon spin currents., Pure spin currents can be generated via thermal excitations of magnons. These magnon spin currents serve as carriers of information in insulating materials, and controlling them using electrical means may enable energy efficient information processing. Here, we demonstrate electric field control of magnon spin currents in the antiferromagnetic insulator Cr2O3. We show that the thermally driven magnon spin currents reveal a spin-flop transition in thin-film Cr2O3. Crucially, this spin-flop can be turned on or off by applying an electric field across the thickness of the film. Using this tunability, we demonstrate electric field–induced switching of the polarization of magnon spin currents by varying only a gate voltage while at a fixed magnetic field. We propose a model considering an electric field–dependent spin-flop transition, arising from a change in sublattice magnetizations via a magnetoelectric coupling. These results provide a different approach toward controlling magnon spin current in antiferromagnets.

Frequency-domain multiplexing is a readout technique for transition edge sensor bolometer arrays used on modern CMB experiments, including the SPT-3G receiver. Here, we present design details and performance measurements for a low-parasitic frequency-domain multiplexing readout. Reducing the parasitic impedance of the connections between cryogenic components provides a path to improving both the crosstalk and noise performance of the readout. Reduced crosstalk will in turn allow higher multiplexing factors. We have demonstrated a factor of two improvement in parasitic resistance compared to SPT-3G hardware. Reduced parasitics also permits operation of lower-resistance bolometers, which enables better optimization of R$_{\rm{bolo}}$ for improved readout noise performance. The prototype system exhibits noise performance comparable to SPT-3G readout hardware when operating SPT-3G detectors., Comment: 7 pages, 4 figures. Submitted to J. Low Temp. Detectors

Frequency-domain multiplexing (fMux) is an established technique for the readout of large arrays of transition edge sensor (TES) bolometers. Each TES in a multiplexing module has a unique AC voltage bias that is selected by a resonant filter. This scheme enables the operation and readout of multiple bolometers on a single pair of wires, reducing thermal loading onto sub-Kelvin stages. The current receiver on the South Pole Telescope, SPT-3G, uses a 68x fMux system to operate its large-format camera of $\sim$16,000 TES bolometers. We present here the successful implementation and performance of the SPT-3G readout as measured on-sky. Characterization of the noise reveals a median pair-differenced 1/f knee frequency of 33 mHz, indicating that low-frequency noise in the readout will not limit SPT-3G's measurements of sky power on large angular scales. Measurements also show that the median readout white noise level in each of the SPT-3G observing bands is below the expectation for photon noise, demonstrating that SPT-3G is operating in the photon-noise-dominated regime., Comment: 9 pages, 5 figures submitted to the Journal of Low Temperature Physics: LTD18 Special Edition

SPT-3G is a polarization-sensitive receiver, installed on the South Pole Telescope, that measures the anisotropy of the cosmic microwave background (CMB) from degree to arcminute scales. The receiver consists of ten 150~mm-diameter detector wafers, containing a total of 16,000 transition-edge sensor (TES) bolometers observing at 95, 150, and 220 GHz. During the 2018-2019 austral summer, one of these detector wafers was replaced by a new wafer fabricated with Al-Mn TESs instead of the Ti/Au design originally deployed for SPT-3G. We present the results of in-lab characterization and on-sky performance of this Al-Mn wafer, including electrical and thermal properties, optical efficiency measurements, and noise-equivalent temperature. In addition, we discuss and account for several calibration-related systematic errors that affect measurements made using frequency-domain multiplexing readout electronics., Comment: 9 pages, 5 figures, submitted to the Journal of Low Temperature Physics: LTD18 Special Edition

We have developed a new transition-edge sensor material with critical temperature (Tc) in the range 100–200 mK. The new material is a solid solution of two superconducting components, MoxNb1−x, co-sputtered from two high-purity single-component targets (Mo and Nb). The Tc has a minimum (dTc/dx = 0) at an intermediate concentration of the components. We have optimized the deposition parameters and composition to provide films with a sharp superconducting transition at ~ 150 mK. We investigated structural features of the films and surface morphology using X-ray diffraction (XRD) and scanning electron microscopy. The XRD measurements indicate that the grown films are polycrystalline, with a preferred orientation along the (110) crystal direction and a clear correlation between superconducting properties and film microstructure.

We report phased-resolved ferromagnetic resonance (FMR) measurements in an epitaxial Fe50Co50 thin film using a heterodyne, optical detection method. We track the evolution of the precessional phase across the saturated and unsaturated regimes along the FeCo hard axis. For the two regimes, opposite phase evolutions with frequency are observed, which coincide with the negative effective field dependence on the biasing field for the unsaturated modes. In addition, a nonzero phase advance between 0.2 and 0.4 rad is found for the saturated with respect to the unsaturated modes, which indicates an incomplete spatial overlap of the two modes in the film caused by surface pinning effect. The optical method has the advantage of resolving both the spatial and phase information in FMR measurements, which will be closely relevant and adaptable to epitaxial samples with multiple anisotropy axes, and for both flip-chip-based continuous films and spin-torque-based nano-devices.

The antiferromagnetic kagome semimetals Mn3X (X = Ge, Sn, Ga) are of great interest due to properties arising from their Berry curvature, such as large anomalous Nernst and anomalous Hall coefficients, and spin to charge conversion efficiencies at ambient temperatures. However, the synthesis of epitaxial thin films of Mn3Ge in the desired hexagonal phase has been challenging because they do not wet insulating substrates, necessitating the use of a metallic buffer layer. Furthermore, a ferrimagnetic tetragonal phase also forms readily under typical growth conditions, interfering with hexagonal phase properties. We have synthesized atomically smooth and continuous epitaxial thin films of hexagonal Mn3Ge directly on insulating LaAlO3 (111) substrates using electron beam assisted molecular beam epitaxy, using a three-step process that mitigates the formation of the tetragonal phase. The anomalous Nernst coefficient is found to be more than six times larger in our films than in sputtered thin films of Mn3Ge and significantly larger than that of Fe. Our approach can be used to grow thin layers of kagome materials, without interference from a buffer layer in transport properties, and may be applicable to a broader range of materials with large surface energies that do not grow readily on insulating substrates.

Spin torque is a promising tool for driving magnetization dynamics for novel computing technologies. These torques can be easily produced by spin-orbit effects, but for most conventional spin source materials, a high degree of crystal symmetry limits the geometry of the spin torques produced. Magnetic ordering is one way to reduce the symmetry of a material and allow exotic torques, and antiferromagnets are particularly promising because they are robust against external fields. We present spin torque ferromagnetic resonance measurements and second harmonic Hall measurements characterizing the spin torques in antiferromagnetic iron rhodium alloy. We report extremely large, strongly temperature-dependent exotic spin torques with a geometry apparently defined by the magnetic ordering direction. We find the spin torque efficiency of iron rhodium to be (330$\pm$150) % at 170 K and (91$\pm$32) % at room temperature. We support our conclusions with theoretical calculations showing how the antiferromagnetic ordering in iron rhodium gives rise to such exotic torques., 21 pages, 6 figures

We present measurements of the $E$-mode ($EE$) polarization power spectrum and temperature-$E$-mode ($TE$) cross-power spectrum of the cosmic microwave background using data collected by SPT-3G, the latest instrument installed on the South Pole Telescope. This analysis uses observations of a 1500 deg$^2$ region at 95, 150, and 220 GHz taken over a four month period in 2018. We report binned values of the $EE$ and $TE$ power spectra over the angular multipole range $300 \le \ell < 3000$, using the multifrequency data to construct six semi-independent estimates of each power spectrum and their minimum-variance combination. These measurements improve upon the previous results of SPTpol across the multipole ranges $300 \le \ell \le 1400$ for $EE$ and $300 \le \ell \le 1700$ for $TE$, resulting in constraints on cosmological parameters comparable to those from other current leading ground-based experiments. We find that the SPT-3G dataset is well-fit by a $\Lambda$CDM cosmological model with parameter constraints consistent with those from Planck and SPTpol data. From SPT-3G data alone, we find $H_0 = 68.8 \pm 1.5 \mathrm{km\,s^{-1}\,Mpc^{-1}}$ and $\sigma_8 = 0.789 \pm 0.016$, with a gravitational lensing amplitude consistent with the $\Lambda$CDM prediction ($A_L = 0.98 \pm 0.12$). We combine the SPT-3G and the Planck datasets and obtain joint constraints on the $\Lambda$CDM model. The volume of the 68% confidence region in six-dimensional $\Lambda$CDM parameter space is reduced by a factor of 1.5 compared to Planck-only constraints, with only slight shifts in central values. We note that the results presented here are obtained from data collected during just half of a typical observing season with only part of the focal plane operable, and that the active detector count has since nearly doubled for observations made with SPT-3G after 2018.

PdO, widely used in catalysis in powder form for decades, has been predicted recently to be a Dirac semimetal. Synthesis of high-quality single crystals of this material is thus of great interest. Here, by using ozone-assisted molecular beam epitaxy, PdO thin films were grown on a MgO (001) substrate. X-ray diffraction and transmission electron microscopy indicate the film is $a/b$ axis oriented, with the $c$ axis lying in plane. Fully oxygenated PdO films have a low density of holelike carriers, and are insulating at the lowest temperatures. Our density functional theory calculations using the Heyd-Scuseria-Ernzerhof exchange-correlation functional suggest a \ensuremath{\sim}1.0 eV band gap at the $M$ point, where the gap can be reduced by tensile strain along the $c$ axis and the bands begin to invert when the tensile strain is as high as 18%. Although tensile strain of this magnitude is experimentally not viable using epitaxy, electrons can be doped by oxygen reduction. Our results emphasize the need for careful consideration of electron correlation effects and stoichiometry in ab initio modeling of topological semimetals involving transition metal oxides.

A superconducting diode is an electronic device that conducts supercurrent and exhibits zero resistance primarily for one direction of applied current. Such a dissipationless diode is a desirable unit for constructing electronic circuits with ultralow power consumption. However, realizing a superconducting diode is fundamentally and technologically challenging, as it usually requires a material structure without a centre of inversion, which is scarce among superconducting materials. Here, we demonstrate a superconducting diode achieved in a conventional superconducting film patterned with a conformal array of nanoscale holes, which breaks the spatial inversion symmetry. We showcase the superconducting diode effect through switchable and reversible rectification signals, which can be three orders of magnitude larger than that from a flux-quantum diode. The introduction of conformal potential landscapes for creating a superconducting diode is thereby proven as a convenient, tunable, yet vastly advantageous tool for superconducting electronics. This could be readily applicable to any superconducting materials, including cuprates and iron-based superconductors that have higher transition temperatures and are desirable in device applications., 25 pages, 4 figures

Antiferromagnets are beneficial for future spintronic applications due to their zero magnetic moment and ultrafast dynamics. But gaining direct access to their antiferromagnetic order and identifying the properties of individual magnetic sublattices, especially in thin films and small-scale devices, remains a formidable challenge. So far, the existing read-out techniques such as anisotropic magnetoresistance, tunneling anisotropic magnetoresistance, and spin-Hall magnetoresistance, are even functions of sublattice magnetization and thus allow us to detect different orientations of the N\'eel order for antiferromagnets with multiple easy axes. In contrast direct electrical detection of oppositely oriented spin states along the same easy axes (e.g., in uniaxial antiferromagnets) requires sensitivity to the direction of individual sublattices and thus is more difficult. In this study, using spin Seebeck effect, we report the electrical detection of the two sublattices in a uniaxial antiferromagnet Cr2O3. We find the rotational symmetry and hysteresis behavior of the spin Seebeck signals measured at the top and bottom surface reflect the dierction of the surface sublattice moments, but not the N\'eel order or the net moment in the bulk. Our results demonstrate the important role of interface spin sublattices in generating the spin Seebeck voltages, which provide a way to access each sublattice independently, enables us to track the full rotation of the magnetic sublattice, and distinguish different and antiparallel antiferromagnetic states in uniaxial antiferromagnets.

We demonstrate the electrical detection of magnon-magnon hybrid dynamics in yttrium iron garnet/permalloy (YIG/Py) thin film bilayer devices. Direct microwave current injection through the conductive Py layer excites the hybrid dynamics consisting of the uniform mode of Py and the first standing spin wave ($n=1$) mode of YIG, which are coupled via interfacial exchange. Both the two hybrid modes, with Py or YIG dominated excitations, can be detected via the spin rectification signals from the conductive Py layer, providing phase resolution of the coupled dynamics. The phase characterization is also applied to a nonlocally excited Py device, revealing the additional phase shift due to the perpendicular Oersted field. Our results provide a device platform for exploring hybrid magnonic dynamics and probing their phases, which are crucial for implementing coherent information processing with magnon excitations

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. Exchange bias effects have been studied in elliptical dots composed of ferromagnetic Ni80Fe20-antiferromagnetic Ir20Mn80 bilayers. The magnetization reversal mechanisms and magnetic configurations have been investigated by magneto-optic Kerr effect and magnetic force microscopy. Although the obtained bias fields in these dots are relatively small, the magnetization reversal is found to be influenced by the ferromagnetic-antiferromagnetic coupling. Namely, for some off-axis angles of measurement, the magnetization reversal mechanism of the Ni80Fe20-Ir20Mn80 ellipses depends on whether exchange bias is induced along the minor or major axis of the ellipses. Hence, exchange bias is shown to be an effective means for tailoring the magnetization reversal of elliptical dots after sample fabrication.

A superconducting Transition-Edge Sensor (TES) with low-$T_c$ is essential in a high resolution calorimetric detection. With a motivation of developing sensitive calorimeters for applications in cryogenic neutrinoless double beta decay searches, we have been investigating methods to reduce the $T_c$ of an Ir film down to 20 mK. Utilizing the proximity effect between a superconductor and a normal metal, we found two room temperature fabrication recipes of making Ir-based low-$T_c$ films. In the first approach, an Ir film sandwiched between two Au films, a Au/Ir/Au trilayer, has a tunable $T_c$ in the range of 20-100 mK depending on the relative thicknesses. In the second approach, a paramagnetic Pt thin film is used to create Ir/Pt bilayer with a tunable $T_c$ in the same range. We present detailed study of fabrication and characterization of Ir-based low-$T_c$ films, and compare the experimental results to theoretical models. We show that Ir-based films with predictable and reproducible critical temperature can be consistently fabricated for use in large scale detector applications., 5 figures, accepted in the Journal of Applied Physics

Direct detection of phonons is important for the investigation of information interconversion between the resonantly coupled magnons and phonons. Here we report resonant coupling of magnons and phonons, which can be directly visualized by using micro focused Brillouin light scattering in Ni/LiNbO3 hybrid heterostructures. The patterns of surface acoustic wave phonons, originating from the interference between the original wave {\psi}0(A_0,k) and reflected wave {\psi}1(A_1,-k), can be modulated by magnetic field due to the magnon-phonon coupling. By analyzing the information of phonons obtained from Brillouin spectroscopy, the properties of the magnon system (Ni film), e.g., ferromagnetic resonance field and resonance linewidth can be determined. The results provide spatially resolved information about phonon manipulation and detection in a coupled magnon-phonon system., Comment: 4 figures,11 pages

We demonstrate the magnetically-induced transparency (MIT) effect in Y$$_3$$ 3 Fe$$_5$$ 5 O$$_{12}$$ 12 (YIG)/Permalloy (Py) coupled bilayers. The measurement is achieved via a heterodyne detection of the coupled magnetization dynamics using a single wavelength that probes the magneto-optical Kerr and Faraday effects of Py and YIG, respectively. Clear features of the MIT effect are evident from the deeply modulated ferromagnetic resonance of Py due to the perpendicular-standing-spin-wave of YIG. We develop a phenomenological model that nicely reproduces the experimental results including the induced amplitude and phase evolution caused by the magnon–magnon coupling. Our work offers a new route towards studying phase-resolved spin dynamics and hybrid magnonic systems.

The resonant coupling of phonons and magnons is important for the interconversion of phononic and spin degrees of freedom. We studied the phonon transmission in LiNbO3 manipulated by the dynamic magnetization in a Ni thin film. It was observed that the phonons could be absorbed strongly through resonant magnon-phonon coupling, which was realized by optimizing the interfacial coupling between Ni and LiNbO3. The line shapes of phonon transmission were further investigated considering the magnon-phonon interconversion in the elastically driven ferromagnetic resonance process. The results promote unique routes for phonon manipulation and detection in the presence of magnetization dynamics., Comment: 14 pages, 5 figures

The South Pole Telescope SPT-3G camera utilizes Ti/Au transition edge sensors (TESs). A key requirement for these sensors is reproducibility and long-term stability of the superconducting (SC) transitions. Here, we discuss the impact of electrical contacts design and materials on the shape of the SC transitions. Using scanning electron microscope, atomic force microscope, and optical differential interference contrast microscopy, we observed the presence of unexpected defects of morphological nature on the titanium surface and their evolution in time in proximity to Nb contacts. We found direct correlation between the variations of the morphology and the SC transition shape. Experiments with different diffusion barriers between TES and Nb leads were performed to clarify the origin of this problem. We have demonstrated that the reproducibility of superconducting transitions can be significantly improved by preventing diffusion processes in the TES–leads contact areas.

In this work, we have measured the properties of membrane-suspended bolometer thermal links and microstrip transmission lines in the transition-edge sensor arrays for the third-generation camera for South Pole Telescope (SPT-3G). A promising technique for controlling the end point of the release etch that defines the thermal link has been developed. We have also evaluated the microstrip loss in our detectors by measuring the optical efficiency of detectors with different lengths of microstrip line. The loss tangent is sufficiently low for the use in multi-chronic pixels for cosmic microwave background instruments like SPT-3G.

The demand for hybrid microelectronic systems has arisen because of the trend toward miniaturization of devices, in particular in lab-on-a-chip devices for biomedicine. This paper aims to describe the development of microelectromagnetic structures for the manipulation of biological cells. An innovative, low-cost, and highly practical approach based on the use of parallel conductive wires is described. The types of connection and their effect on magnetic field shape were investigated with simulations. The strategy to estimate the required concentration of nanoparticles and applied current to trap biological cells was discussed, and tests were carried using an red fluorescent protein (RFP)-modified mouse melanoma cell line (B16 RFP). The prospects and efficiency of such technology of microwire production are demonstrated.

The third-generation upgrade to the receiver on the South Pole Telescope, SPT-3G, was installed at the South Pole during the 2016–2017 austral summer to measure the polarization of the cosmic microwave background. Increasing the number of detectors by a factor of 10 to ∼16,000 \ud ∼16,000\ud required the multiplexing factor to increase to 68 and the bandwidth of the frequency-division readout electronics to span 1.6–5.2 MHz. This increase necessitates low-thermal conductance, low-inductance cryogenic wiring. Our cold readout system consists of planar thin-film aluminum inductive–capacitive resonators, wired in series with the detectors, summed together, and connected to 4K SQUIDs by 10−μm \ud 10−μm\ud -thick niobium–titanium (NbTi) broadside-coupled striplines. Here, we present an overview of the cold readout electronics for SPT-3G, including assembly details and characterization of electrical and thermal properties of the system. We report, for the NbTi striplines, values of R≤10 −4 Ω \ud R≤10−4Ω\ud , L=21±1 nH \ud L=21±1 nH\ud , and C=1.47±.02 nF \ud C=1.47±.02 nF\ud . Additionally, the striplines’ thermal conductivity is described by kA=6.0±0.3 T 0.92±0.04 μW mm K −1 \ud kA=6.0±0.3 T0.92±0.04 μW mm K−1\ud . Finally, we provide projections for cross talk induced by parasitic impedances from the stripline and find that the median value of percentage cross talk from leakage current is 0.22 and 0.09% \ud 0.09%\ud from wiring impedance.

The South Pole Telescope third-generation (SPT-3G) receiver was installed during the austral summer of 2016–2017. It is designed to measure the cosmic microwave background across three frequency bands centered at 95, 150, and 220 GHz. The SPT-3G receiver has ten focal plane modules, each with 269 pixels. Each pixel features a broadband sinuous antenna coupled to a niobium microstrip transmission line. In-line filters define the desired band-passes before the signal is coupled to six bolometers with Ti/Au/Ti/Au transition edge sensors (three bands × \ud ×\ud two polarizations). In total, the SPT-3G receiver is composed of 16,000 detectors, which are read out using a 68× \ud ×\ud frequency-domain multiplexing scheme. In this paper, we present the process employed in fabricating the detector arrays.

High resolution total internal reflection (TIRF) microscopy (TIRFM) together with detailed computational modeling provides a powerful approach towards the understanding of a wide range of Ca2+ signals mediated by the ubiquitous inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) channel. Exploiting this fruitful collaboration further requires close agreement between the models and observations. However, elementary Ca2+ release events, puffs, imaged through TIRFM do not show the rapid single-channel openings and closings during and between puffs as are present in simulated puffs using data-driven single channel models. TIRFM also shows a rapid equilibration of 10ms after a channel opens or closes which is not achievable in simulation using standard Ca2+ diffusion coefficients and reaction rates between indicator dye and Ca2+. Furthermore, TIRFM imaging cannot decipher the depth of the channel with respect to the microscope, which will affect the change in fluorescence that the microscope detects, thereby affecting its sensitivity to fast single-channel activity. Using the widely used Ca2+ diffusion coefficients and reaction rates, our simulations show equilibration rates that are eight times slower than TIRFM imaging. We show that to get equilibrium rates consistent with observed values, the diffusion coefficients and reaction rates have to be significantly higher than the values reported in the literature, and predict the channel depth to be 200-250nm. Finally, we show that with the addition of noise, short events due to 1-2ms opening and closing of channels that are observed in computational models can be missed in TIRFM.

Noncollinear antiferromagnets can have additional spin Hall effects due to the net chirality of their magnetic spin structure, which provides for more complex spin-transport phenomena compared to ordinary nonmagnetic materials. Here we investigated how ferromagnetic resonance of permalloy (${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$) is modulated by spin Hall effects in adjacent epitaxial ${\mathrm{IrMn}}_{3}$ films. We observe a large dc modulation of the ferromagnetic resonance linewidth for currents applied along the [001] ${\mathrm{IrMn}}_{3}$ direction. This very strong angular dependence of spin-orbit torques from dc currents through the bilayers can be explained by the magnetic spin Hall effect where ${\mathrm{IrMn}}_{3}$ provides novel pathways for modulating magnetization dynamics electrically.

We show that a non-Markovian behavior can appear in a type of Markovian multimeric channel. Such a channel consists of N independent subunits, and each subunit has at least one open state and more than one closed state. Suppose the open state of the channel is defined as M out of N subunits in the open state with N>M>0. We show that, although the gating dynamics for each subunit between open and closed states is Markovian, the channel can show a memory behavior of weak anti-cross-correlation between the adjacent open and closed durations. Our study indicates that a non-Markovian binary time series can be obtained from a linear superposition of some independent channel subunits with Markovian gating dynamics.

We present an experimental study of time refraction of spin waves propagating in microscopic waveguides under the influence of time-varying magnetic fields. Using space- and time-resolved Brillouin light scattering microscopy, we demonstrate that the broken translational symmetry along the time coordinate can be used to in- or decrease the energy of spin waves during their propagation. This allows for a broadband and controllable shift of the spin-wave frequency. Using an integrated design of spin-wave waveguide and microscopic current line for the generation of strong, nanosecond-long, magnetic field pulses, a conversion efficiency up to 39% of the carrier spin-wave frequency is achieved, significantly larger compared to photonic systems. Given the strength of the magnetic field pulses and its strong impact on the spin-wave dispersion relation, the effect of time refraction can be quantified on a length scale comparable to the spin-wave wavelength. Furthermore, we utilize time refraction to excite spin-wave bursts with pulse durations in the nanosecond range and a frequency shift depending on the pulse polarity., Comment: 5 pages, 4 figures

Synthesis of crystallographically well-defined thin films of topological materials is important for unraveling their mesoscale quantum properties and for device applications. Mn$_3$Ge, an antiferromagnetic Weyl semimetal with a chiral magnetic structure on a Kagome lattice, is expected to have enhanced Berry curvature around Weyl nodes near the Fermi energy, leading to large anomalous Hall / Nernst effects and a large spin-Hall effect. Using magnetron sputtering, we have grown epitaxial thin films of hexagonal D0$_{19}$ Mn$_3$Ge that are flat and continuous. Large anomalous Nernst and inverse spin-Hall effects are observed in thermoelectric and spin-pumping devices. The anomalous Nernst signal in our Mn$_3$Ge films is estimated to be 0.1 $\mu$V / K, and is comparable to that in ferromagnetic Fe, despite Mn$_3$Ge having a weak magnetization of ~3.5 m$\mu_B$ at room temperature. The spin mixing conductance is 90.5 nm$^{-2}$ at the Py / Mn$_3$Ge interface, and the spin-Hall angle in Mn$_3$Ge is estimated to be about 8 times of that in Pt., Comment: 25 pages, 5 figures

Noncollinear antiferromagnets can have additional spin Hall effects due to the net chirality of their magnetic spin structure, which provides for more complex spin-transport phenomena compared to ordinary nonmagnetic materials. Here we investigated how ferromagnetic resonance of permalloy (Ni_{80}Fe_{20}) is modulated by spin Hall effects in adjacent epitaxial IrMn_{3} films. We observe a large dc modulation of the ferromagnetic resonance linewidth for currents applied along the [001] IrMn_{3} direction. This very strong angular dependence of spin-orbit torques from dc currents through the bilayers can be explained by the magnetic spin Hall effect where IrMn_{3} provides novel pathways for modulating magnetization dynamics electrically.

Spin waves are promising candidates for information processing and transmission in a broad frequency range. In the realization of magnonic devices, the frequency depended division of the spin wave frequencies is a critical function for parallel information processing. In this work, we demonstrate a proof-of-concept spin-wave frequency division multiplexing method by magnetizing a homogenous magnetic microstripe with an inhomogeneous field. The symmetry breaking additional field is introduced by a permalloy stripe simply placed in lateral proximity to the waveguide. Spin waves with different frequencies can propagate independently, simultaneously and separately in space along the shared waveguide. This work brings new potentials for parallel information transmission and processing in magnonics., 9 pages, 4 figures

In recent years terahertz (THz) technology has been an emerging research field with a broad range of applications. THz radiation falls between the infrared and microwave radiation in the electromagnetic spectrum. Most THz sources to date are not related to the spin degree of freedom; however, recent research efforts in spintronics and ferromagnetism demonstrated that the electron spin offers completely new opportunities for the generation of ultrafast photocurrents. For instance, magnetic heterostructures are very easy to pattern and potentially allow to tailor THz emission characteristics by design. Here, we demonstrate that an ultrafast spin-current pulse driven by a femtosecond laser pulse can create THz transients in microstructured magnetic heterostructures due to the inverse spin Hall effect. We compare the THz electric field and the THz spectrum of a control CoFeB/Pt film with microstructured CoFeB/Pt wires as well as microstructured CoFeB/MgO wires patterned on an extended Pt film. We find that the THz electric field amplitude is proportional to the coverage of the CoFeB/Pt heterostructure on top of the MgO substrate. Furthermore, we analyze the magnetization direction dependence of the THz transients with respect to the easy axis of the ferromagnetic wire. The presented results are the first steps towards shaping and controlling the THz properties by microstructuring of spintronics-based THz emitters.

In the emerging field of magnonics, spin waves are considered for information processing and transmission at high frequencies. Towards this end, the manipulation of propagating spin waves in nanostructured waveguides for novel functionality has recently been attracting increasing focus of research. Excitations with uniform magnetic fields in such waveguides favors symmetric spin wave modes with odd quantization numbers. Interference between multiple odd spin wave modes leads to a periodic self-focusing effect of the propagating spin waves. Here we demonstrate, how antisymmetric spin wave modes with even quantization numbers can be induced by local magnetic fields in a well-controlled fashion. The resulting interference patterns are discussed within an analytical model and experimentally demonstrated using microfocused Brillouin light scattering ({\mu}-BLS)., Comment: 18 pages, 9 figures

The charge and spin of the electrons in solids have been extensively exploited in electronic devices and in the development of spintronics. Another attribute of electrons—their orbital nature—is attracting growing interest for understanding exotic phenomena and in creating the next-generation of quantum devices such as orbital qubits. Here, we report on orbital-flop induced magnetoresistance anisotropy in CeSb. In the low temperature high magnetic-field driven ferromagnetic state, a series of additional minima appear in the angle-dependent magnetoresistance. These minima arise from the anisotropic magnetization originating from orbital-flops and from the enhanced electron scattering from magnetic multidomains formed around the first-order orbital-flop transition. The measured magnetization anisotropy can be accounted for with a phenomenological model involving orbital-flops and a spin-valve-like structure is used to demonstrate the viable utilization of orbital-flop phenomenon. Our results showcase a contribution of orbital behavior in the emergence of intriguing phenomena., The orbital degree of freedom can be as important as the charge and spin of the electron to the electronic phenomena. Here the authors show additional minimum in the angle-dependent magnetoresistance (MR) for the low temperature high magnetic field driven ferromagnetic state in CeSb which indicates the orbital flop induced MR anisotropy.

Antiferromagnetic oxides have recently gained much attention because of the possibility to manipulate electrically and optically the Néel vectors in these materials. Their ultrafast spin dynamics, long spin diffusion length and immunity to large magnetic fields make them attractive candidates for spintronic applications. Additionally, there have been many studies on spin wave and magnon transport in single crystals of these oxides. However, the successful applications of the antiferromagnetic oxides will require similar spin transport properties in thin films. In this work, we systematically show the sputtering deposition method for two uniaxial antiferromagnetic oxides, namely Cr2O3 and α-Fe2O3, on A-plane sapphire substrates, and identify the optimized deposition conditions for epitaxial films with low surface roughness. We also confirm the antiferromagnetic properties of the thin films. The deposition method developed in this article will be important for studying the magnon transport in these epitaxial antiferromagnetic thin films.

Materials with a layered Kagome lattice are expected to give rise to novel physics arising from band structures with topological properties, spin liquid behavior and the formation of skyrmions. Until now, most work on Kagome materials has been performed on bulk samples due to difficulties in thin film synthesis. Here, by using molecular beam epitaxy, layered Kagome-structured FeSn films are synthesized on (111) oriented LaAlO3 substrate. Both in-situ and ex-situ characterizations indicate these films are highly crystalline and c-axis oriented, with atomically smooth surfaces. However, the films grow as disconnected islands, with lateral dimensions on the micron scale. By patterning Pt electrodes using a focused electron beam, longitudinal and transverse resistance of single islands have been measured in magnetic fields. Our work opens a pathway for exploring mesoscale transport properties in thin films of Kagome materials and related devices.

Detecting the local amplitude and phase of magnetization excitations (spin waves) is important for coherent spin information processing. Phase detection traditionally is either via electrically rectified signals, or by pump-probe optical and x-ray methods. In this work, the authors demonstrate tabletop, heterodyne optical detection of the local phase of ferromagnetic resonance, with the capability to extract spin-orbit torques by quantifying an additional precessional phase in a heavy-metal/ferromagnet bilayer. The results offer spin-torque magnetometry with spatial and phase resolution, for studying electrically driven magnetization dynamics in spintronic nanodevices.