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To realize spin wave logic gates, programable phase inverters are essential. We image using phase-resolved Brillouin light scattering microscopy propagating spin waves in a one-dimensional magnonic crystal consisting of dipolarly coupled magnetic nanostripes. We demonstrate phase shifts upon a single nanostripe of opposed magnetization. Using micromagnetic simulations, we model our experimental finding in a wide parameter space of biasfields and wave vectors. We find that low-loss phase inversion is achieved, when the internal field of the oppositely magnetized nanostripe is tuned such that the latter supports a resonant standing spin wave mode with an odd quantization number at the given frequency. Our results are key for the realization of phase inverters with optimized signal transmission. [ABSTRACT FROM AUTHOR]

Presents a study that measured the magnetic inductance of an yttrium-based square washer superconducting quantum interference devices. Methodology; Analysis of the temperature dependance of inductance; Impact of inductance on device performance.

We performed broadband spin-wave spectroscopy on 200 nm thick yttrium iron garnet containing arrays of partially embedded magnetic nanodisks. Using integrated coplanar waveguides (CPWs), we studied the excitation and transmission of spin waves depending on the presence of nanomagnet arrays of different lateral extensions. By means of the grating coupler effect, we excited spin waves propagating in multiple lateral directions with wavelengths down to 111 nm. They exhibited group velocities of up to 1 km/s. Detection of such short-wavelength spin waves was possible only in symmetrically designed emitter/detector configurations, not with a bare CPW. We report spin waves propagating between grating couplers under oblique angles exhibiting a wave vector component parallel to the CPW. The effective propagation distance amounted to about 80 μm. Such transmission signals were not addressed before and substantiate the versatility of the grating coupler effect for implementing nanomagnonic circuits. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Optically reconfigurable magnetic materials" by Marc Vogel and colleagues that is published in the previous issue.

This article was originally published online on 20 April 2021 with the word programmable incorrectly spelled in the title and the text. Publisher's Note: "Bistable nanomagnet as programmable phase inverter for spin waves" [Appl. Phys Lett. All online versions of the article were corrected on 27 April 2021. [Extracted from the article]

Examines the spin degeneracy of the Landau levels in magnetization measurements on a two-dimensional electron system (2DES). Use of a superconducting quantum interference device; Performance of magnetic measurements in aluminum gallium arsenide (GaAs)/GaAs heterostructures; Reference to the oscillatory magnetic moment of 2DES as a function of gate voltage.

Review: 15 refs. [ABSTRACT FROM AUTHOR]

Aperiodicity and un-conventional rotational symmetries allow quasicrystalline structures to exhibit unusual physical and functional properties. In magnetism, artificial ferromagnetic quasicrystals exhibited knee anomalies suggesting reprogrammable magnetic properties via non-stochastic switching. However, the decisive roles of short-range exchange and long-range dipolar interactions have not yet been clarified for optimized reconfigurable functionality. We report broadband spin-wave spectroscopy and X-ray photoemission electron microscopy on different quasicrystal lattices consisting of ferromagnetic Ni81Fe19 nanobars arranged on aperiodic Penrose and Ammann tilings with different exchange and dipolar interactions. We imaged the magnetic states of partially reversed quasicrystals and analyzed their configurations in terms of the charge model, geometrical frustration and the formation of flux-closure loops. Only the exchange-coupled lattices are found to show aperiodicity-specific collective phenomena and non-stochastic switching. Both, exchange and dipolarly coupled quasicrystals show magnonic excitations with narrow linewidths in minor loop measurements. Thereby reconfigurable functionalities in spintronics and magnonics become realistic. Artificial spin ices, consisting of an array of geometrically aligned nanobars, can be used to engineer aperiodic arrays that mimic quasicrystalline structures and their physical properties. Here, the authors prepare artificial magnetic quasicrystals and investigate the exchange and dipolar interactions using X-ray photoemission electron microscopy and broadband spin-wave spectroscopy, where the results suggest reconfigurable magnetic orientations. [ABSTRACT FROM AUTHOR]

Using conventional coplanar waveguides (CPWs), we excited spin waves with a wavelength λ down to 310 nm in a 200 nm thin yttrium iron garnet film grown by liquid phase epitaxy. Spinwave transmission was detected between CPWs that we separated by up to 2mm. For magnetostatic surface spin waves, we found a large nonreciprocity of 0.9 and a high group velocity vg of up to 5.4 km/s. The extracted decay length ld amounted to 0.86 mm. Small λ, high vg, and large ld are key figures of merit when aiming at non-charged based signal transmission and logic devices with spin waves. [ABSTRACT FROM AUTHOR]

Electromagnetic metasurfaces modulate a material's response to electromagnetic waves by specifically arranged elements with dimensions below the wavelength. They have opened new fields of research, including flat optics and nanophotonics on a chip. Ferromagnetic metasurfaces could become the building blocks for manipulation of both microwaves and spin waves (magnons). So far, the functionality of magnonic devices has been limited by high intrinsic damping of the materials employed, suppressing long‐distance spin‐wave propagation. Here ferromagnetic metasurfaces are reported, which are created from periodic arrays of either 15 nm thick Co20Fe60B20, Ni80Fe20 or Co nanodisks on ferrimagnetic yttrium iron garnet (YIG) hosting topologically protected vortex states. This device, a reconfigurable spectral filter, operates in the microwave regime near 0.9 GHz and manipulates long‐distance spin‐wave transmission in thin YIG. An efficiency of 98.5% is demonstrated, with the metasurface covering only 15% of the microwave antenna. This first demonstration of a ferromagnetic metasurface opens unprecedented possibilities for on‐chip control of microwaves in low‐damping ferrimagnetic insulators. [ABSTRACT FROM AUTHOR]

Magnetic resonance techniques at nuclei and electrons are applied to characterize the electronic structure and collective magnetic excitations throughout the magnetic phase diagrams of the lacunar spinels GaV4S8 and GaV4Se8 showing cycloidal, Néel‐type skyrmion lattice and ferromagnetically polarized phases. 71Ga nuclear magnetic resonance (NMR) provides a local probe of the rhombohedral distortion and the resulting uniaxial magnetic anisotropy via the detection of electric field gradients (EFGs) and hyperfine coupling at the gallium sites of these lacunar spinels. Broadband electron spin resonance (ESR) allows identifying clockwise, counterclockwise, and breathing modes of the skyrmion‐lattice phase supported by theoretical simulations. [ABSTRACT FROM AUTHOR]

Thermoelectric effects in microstructured permalloy (Py)/Au wires are investigated using space- and time-resolved measurements based on scanning focused laser heating. Supported by numerical simulations of the temperature distribution, we identify two major contributions to the laser-induced signals: (i) the Seebeck effect due to thermocouples of Py/Au and (ii) the anomalous Nernst effect (ANE) in Py with a coefficient of NANE≈1.6 μV/K. ANE-based magnetic imaging of magnetic domains and magnetization reversal is demonstrated with a lateral resolution on the μm scale. [ABSTRACT FROM AUTHOR]

118, 172403 (2021).10.1063/5.0045855 32 S. Finizio, S. Wintz, S. Mayr, A. J. Huxtable, M. Langer, J. Bailey, G. Burnell, C. H. Marrows, and J. Raabe, " Time-resolved visualization of the magnetization canting induced by field-like spin-orbit torques", Appl. Phys. This might be achieved, for instance, by means of radio frequency filters based on mesoscopic spin-wave cavities[43] or circulators enabled by chiral spin-wave routing across two stacked ferromagnetic layers without interlayer exchange coupling.[44] Magnetization dynamics in synthetic antiferromagnets, i.e., acoustic and optical magnons in layers with interlayer-exchange coupling, are considered theoretically by Dai and Ma[45] and Jeffrey I et al. i [46] Aiming at magnonic platforms for devices exploiting hybridized quantum excitations, they predict strong magnon-magnon coupling in tilted fields and a suppressed exceptional point, respectively. 118, 242403 (2021).10.1063/5.0050872 26 M. Schöbitz, S. Finizio, A. D. Riz, J. Hurst, C. Thirion, D. Gusakova, J.-C. Toussaint, J. Bachmann, J. Raabe, and O. Fruchart, " Time-resolved imaging of Œrsted field induced magnetization dynamics in cylindrical magnetic nanowires", Appl. Phys. In addition, non-linear magnetization dynamics through the effect of magnetic fields, spin currents, voltages, or optical pulses in confined magnetic dots transforms information by switching, tilting, deforming, or exciting the magnetization locally. [Extracted from the article]

Tailored nonmagnetic semiconductor-metal hybrid structures exhibit a large magnetoresistance effect in a homogeneous magnetic field. This is the so-called extraordinary magnetoresistance effect. Here, we study numerically the magnetoresistance of such hybrid structures in the inhomogeneous field of a magnetic dot. Surprisingly, the four-point resistance R versus magnetic field B changes its symmetry if compared to the case of a homogeneous field and is strongly dependent on the position of the local magnetic field. Interestingly, the active device area is not defined by the voltage probe separation, but by the positioning of voltage probes and current leads. We find a magnetoresistance effect as large as 18% although only 1/60 of the device area is subject to a small magnetic field of ±50 mT. These results are promising for sensing magnetic-field distributions in the nanoscale regime such as the stray fields of magnetic recording media. [ABSTRACT FROM AUTHOR]

Experimental and theoretical studies have shown that nonmagnetic semiconductor-metal hybrid structures can exhibit a very large magnetoresistance effect, the so-called extraordinary magnetoresistance (EMR) effect. The EMR can be useful in magnetic-field sensors and read heads. We show that the sensitivity of a linear hybrid structure can be further enlarged by using an optimized configuration of current leads and voltage probes. Strikingly, we find that the EMR and the Hall effect cooperate and thereby improve the performance. Our findings also explain the origin of the recently reported sensitivity increase in a nanostructured EMR device obtained via interchanging one lead and one probe [J. Moussa et al., J. Appl. Phys. 94, 1110 (2003)]. [ABSTRACT FROM AUTHOR]

Semiconductor–metal hybrid structures can exhibit a very large geometrical magnetoresistance effect, the so-called extraordinary magnetoresistance (EMR) effect. Using the finite element method, we study the EMR effect in rectangular semiconductor–metal hybrid structures and investigate the effects of material parameters and of device geometry. We find that the EMR device exhibits inverse scalability, i.e., the output characteristics improve with decreasing device width. This is promising for miniaturized magnetic-field sensors like, e.g., read heads. Using realistic device parameters, we predict an optimized performance as a sensor for a width-to-length ratio of 0.025. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Quasicrystalline structures and aperiodic metamaterials find applications ranging from established consumer gadgets to potential high‐tech photonic components owing to both complex arrangements of constituents and exotic rotational symmetries. Magnonics is an evolving branch of magnetism research where information is transported via magnetization oscillations (magnons). Their control and manipulation are so far best accomplished in periodic metamaterials which exhibit properties artificially modulated on the nanoscale. They give rise to functional components, such as band stop filters, magnonic transistors and nanograting couplers. Here, spin‐wave excitations in artificial ferromagnetic quasicrystals created via aperiodic arrangement of nanoholes are studied experimentally. Their ten‐fold rotational symmetry results in multiplexed magnonic nanochannels, suggesting a width down to 50 nm inside a so‐called Conway worm. Key elements of design are emergent magnon motifs and the worm‐like features which are scale‐invariant and not present in the periodic metamaterials. By imaging wavefronts in quasicrystals, insight is gained into how the discovered features materialize as a dense wavelength division multiplexer. [ABSTRACT FROM AUTHOR]

The article reports on science research based on applied science which discusses about nonreciprocal surface acoustic wave propagation via magneto-rotation coupling. Topics include fundamental form of magnonphonon interaction is an intrinsic property of magnetic materials, the magnetoelastic coupling; and form of interaction has been the basis for describing magnetostrictive materials and their applications, where strain induces changes of internal magnetic fields.

A large area array of metal-oxide-metal (MOM) tunneling diodes with an ultrathin dielectric (∼3.6 nm aluminum oxide) have been fabricated via a transfer-printing process. The MOM diodes exhibit an excellent tunneling behavior that is suitable for rectifying high-frequency ac current into direct current (dc). Direct tunneling and Fowler-Nordheim tunneling have been observed over eight orders of magnitude in current density. The ratio between forward and reverse current is as large as two orders of magnitude. Simulations have been carried out to extract the static device parameters and have confirmed the existence of a dipole layer at the aluminum/aluminum oxide interface of the printed tunneling diodes. Capacitance measurements have shown that the permittivity of the ultrathin aluminum oxide film is smaller than that of bulk aluminum oxide. The mechanical yield of the transfer-printing process is better than 80%, confirming that transfer printing is a promising candidate for the efficient fabrication of quantum devices over large areas. [ABSTRACT FROM AUTHOR]

Magnonic crystals are interesting for spin-wave based data processing. We investigate one-dimensional magnonic crystals (1D MCs) consisting of bistable Co 20 Fe 60 B 20 nanostripes separated by 75 nm wide air gaps. By adjusting the magnetic history, we program a single stripe of opposed magnetization in an otherwise saturated 1D MC. Its influence on propagating spin waves is studied via broadband microwave spectroscopy. Depending on an in-plane bias magnetic field, we observe spin wave phase shifts of up to almost π and field-controlled attenuation attributed to the reversed nanostripe. Our findings are of importance for magnetologics, where the control of spin wave phases is essential. [ABSTRACT FROM AUTHOR]

Broadband spin-wave spectroscopy is performed on two arrays of long 300-nm-wide Ni20Fe80 wires which exhibit two different edge-to-edge separations a of 700 and 200 nm. When the in-plane field Hvector is applied a few degrees off from the hard axis direction, an intermediate field regime is found where the central region and the edges of a wire are magnetized in different directions. Here, resonances are pronounced and reflect spin waves confined on the sub-100 nm scale within a wire. For small a, the confinement effect is found to occur over a broad regime of H. These results are relevant for high-density integration of magnonic waveguides. [ABSTRACT FROM AUTHOR]

We have investigated the magnetoresistance of metal-semiconductor hybrid structures at 4.2 K. The devices consisted of polycrystalline Au and an InAs-based heterostructure that hosted a high-mobility two-dimensional electron system. We have varied the electrical parameters and, in particular, the width-to-length ratio W/L of the linear hybrid structures. The recently discovered extraordinary magnetoresistance effect is most pronounced for narrow devices with W/L<=0.05, consistent with our theoretical prediction. Relative resistance changes with a factor of 1000 are observed at 1 T. To achieve this an interface resistance of only 10-8 Ω cm2 is a prerequisite. This can be prepared routinely by in situ cleaved edge overgrowth. [ABSTRACT FROM AUTHOR]

The quantum oscillatory magnetization M(B) and chemical potential µ(B) of a two-dimensional (2D) electron system provide important and complementary information about its ground state energy at low temperature T. We developed a technique that provides both quantities in the same cool-down process via a decoupled static operation and resonant excitation of a micromechanical cantilever. On InGaAs/InP heterostructures, we observed beating patterns in both M(B) and µ(B) attributed to spin-orbit interaction. A significantly enhanced sensitivity in µ enabled us to extract Rashba and Dresselhaus parameters with high accuracy. The technique is powerful for detailed investigations on the electronic properties of 2D materials. [ABSTRACT FROM AUTHOR]

We study the spin dynamics in arrays of densely packed submicron Ni80Fe20 wires which form one-dimensional magnonic crystals. They are subject to an in-plane magnetic field H being collinear with the wires. In the case when neighboring wires are magnetized antiparallel, broadband spin-wave spectroscopy reveals a mode repulsion behavior around a certain field Hmr. We attribute this to dipolar coupling and avoided crossing of resonant modes of individual wires. The modes are found to hybridize across the array and form acoustic and optical modes. When an array of alternating-width wires is considered, Hmr is found to vary characteristically as a function of the width difference Δw of neighboring wires. Interestingly, the sign of Hmr reflects the orientation of the wires magnetization. For our devices we find experimentally frequency splittings δf on the order of 1 GHz between the acoustic and optical mode. We use micromagnetic modeling to analyze spin precession profiles and investigate the hybridization of modes. The simulated splitting is larger than the observed one. We attribute the discrepancy to a reduced dipolar coupling in the real samples. Using a theoretical model which considers the reduced dipolar coupling we analyze δf for different geometrical parameters such as the edge-to-edge separation a and the width difference Δw. Though relevant for Hmr, ΔW is not decisive for δf. Instead, α is key for the frequency splitting. The results are relevant in order to tailor the dynamic response and band structure of magnonic crystals. [ABSTRACT FROM AUTHOR]

Spin-wave (SW) modes are addressed which are confined in thin individual Ni80 Fe20 nanowires with widths ranging from 220 to 360 nm. In periodic arrays with an edge-to-edge separation of down to 100 nm, confined modes of neighboring nanowires are found to couple coherently and form allowed minibands and forbidden frequency gaps. This gives rise to a one-dimensional magnonic crystal. We present all-electrical SW spectroscopy data and micromagnetic simulations. We find that the nanowire arrays allow us to reprogram the relevant magnonic band structure via the magnetic history. A forbidden frequency gap of up to about 1 GHz is controlled by an in-plane magnetic field being as small as a few mT. [ABSTRACT FROM AUTHOR]

We report an experimental investigation of the magnetic normal modes in large-area Ni80Fe20 antidot arrays fabricated on commercially available silicon substrates using deep ultraviolet lithography at 248 nm exposing wavelength. The effect of the lattice symmetry (square, rhombic and honeycomb) on the magnetic normal modes of the arrays has been investigated by both Brillouin light scattering and broadband ferromagnetic resonance using a vector network analyzer. For all the measured samples, the eigenfrequencies show an angular symmetry which is consistent with the lattice arrangement of the holes. Interpretation of the experimental results was achieved by micromagnetic simulations which enabled us to calculate both the frequencies of the modes and the corresponding spatial profile, correlating their angular evolution with the magnetic ground state. [ABSTRACT FROM AUTHOR]

We present a combined experimental investigation of magnetic normal modes in an antidot lattice using both Brillouin light scattering and broadband ferromagnetic resonance. It was fabricated on a silicon substrate using optical ultraviolet lithography. The sample consisted of a 30-mn-thick Ni80 Fe20 squared antidot array with circular holes whose diameter and edge-to-edge spacing are 250 and 150 nm, respectively. Experiments were performed as a function of the applied magnetic field μoHext in the range from -100 to 100 mT, with Hext applied along both the square lattice axis and its diagonal. Several peaks were observed in both the Brillouin light scattering and ferromagnetic resonance spectra, and their evolution with the intensity and the direction of the applied field Hext was measured. Micromagnetic simulations enabled us to identify the modes in terms of their symmetry obtaining a good quantitative agreement with the measured frequencies. In addition, we show how the inhomogeneity of the internal field affected the properties of the magnetic eigen. modes and their localization in different regions of the antidot lattice. [ABSTRACT FROM AUTHOR]

For understanding magnonic materials the fundamental characterization of their frequency response is essential. However, determining full dispersion relations and real space wavelength measurements are challenging and time-consuming tasks. We present an approach for spin wave excitation by a modified Sinc pulse, which combines a cosine signal with a conventional Sinc function. The resulting adjustable frequency bands lead to a broadband spin wave excitation at uniform power levels. Subsequently, time resolved scanning transmission X-ray microscopy is used for direct imaging of all excited spin waves in real space. To demonstrate the capabilities of this approach, a modified Sinc excitation of an ultra-thin yttrium-iron-garnet film is shown that simultaneously reveals phase, amplitude, and k-space information from a single measurement. Consequently, this approach allows a fast and thorough access to the full dispersion relation including spatial maps of the individual spin wave modes, enabling complete characterization of magnonic materials down to the nanoscale in real and reciprocal space. [ABSTRACT FROM AUTHOR]

Spin waves can probe the Dzyaloshinskii-Moriya interaction (DMI), which gives rise to topological spin textures, such as skyrmions. However, the DMI has not yet been reported in yttrium iron garnet (YIG) with arguably the lowest damping for spin waves. In this work, we experimentally evidence the interfacial DMI in a 7-nm-thick YIG film by measuring the nonreciprocal spin-wave propagation in terms of frequency, amplitude, and most importantly group velocities using all electrical spin-wave spectroscopy. The velocities of propagating spin waves show chirality among three vectors, i.e., the film normal direction, applied field, and spin-wave wave vector. By measuring the asymmetric group velocities, we extract a DMI constant of 16 μJ/m², which we independently confirm by Brillouin light scattering. Thickness-dependent measurements reveal that the DMI originates from the oxide interface between the YIG and garnet substrate. The interfacial DMI discovered in the ultrathin YIG films is of key importance for functional chiral magnonics as ultralow spin-wave damping can be achieved. [ABSTRACT FROM AUTHOR]

The authors have investigated the effect of stress on the room-temperature magnetism of a 10 nm thick Heusler-alloy film NiMnSb grown epitaxially on InP. Tensile stress, which the authors applied externally along the easy axis using a piezostack, is shown to reduce the coercivity and the anisotropy coefficient. Using broadband ferromagnetic resonance measurements, the authors find that a relative variation in the lattice constant as small as 0.08% changes the in-plane uniaxial anisotropy by 20%. This explains the significant variation of anisotropy with film thickness, which was recently reported for NiMnSb. [ABSTRACT FROM AUTHOR]