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It has been shown previously that spin-Hall oscillators based on current-driven bi-layered film structures containing an antiferromagnet (AFM) and a normal metal can generate ultra-short (∼ 2 ps) "spike-like" pulses in response to an external current stimulus of a sufficient amplitude, thus operating as ultra-fast artificial "neurons." Here, we report the results of numerical simulations demonstrating that a single AFM "neuron" can perform the logic functions of or, and, majority, or q-gates, while a circuit consisting of a small number n < 5 of AFM "neurons" can function as a full-adder or as a dynamic memory loop with variable clock frequency. The clock frequencies of such AFM-based logic devices could reach tens of GHz, which make them promising as base elements of future ultra-fast high-efficiency neuromorphic computing. [ABSTRACT FROM AUTHOR]

The development of a multiple method to model acoustic wave propagation in a medium containing several hollow cylinders-a microstructural acoustic fiber (MAF) is described. The method could be applied to calculate the wave dispersion of the wave propagating along a structure with 18 hollow cylinders.

An analog microwave signal correlator, based on parametric pumping of a spin wave by a radio frequency (RF) magnetic field, is demonstrated. The binary codes to be correlated modulate the two microwave signals input to the device to, respectively, excite the spin wave and RF field at twice the carrier frequency of the spin wave. The magnetic field parametrically pumps the spin wave, generating a counterpropagating idler spin wave, the modulation of which is the cross-correlation of the binary codes. In the experimental device implemented, correlation of codes up to 16 chips in length at a spin-wave carrier frequency of 1.2 GHz is demonstrated. The code length is limited by the time available for the parametric interaction as well as the signal bandwidth of the device. Process gain, which quantifies the performance of the correlator in recognizing a given code and rejecting interfering codes, is determined for shorter codes and found to be close to the theoretical maximum for each length. The correlator efficiency, with a bilinearity coefficient of –79 dBm, is poor. However, there remains a significant scope for optimization of the experimental device so that correlation of longer codes with improved efficiency will be possible. [ABSTRACT FROM AUTHOR]

A spin-torque nano-oscillator (STNO) driven by a ramped bias current can perform spectrum analysis quickly over a wide frequency bandwidth. The STNO spectrum analyzer operates by injection locking to external microwave signals and produces an output dc voltage V\mathrm{ dc} that temporally encodes the input spectrum. We found, via numerical analysis with a macrospin approximation, that an STNO is able to scan a 10 GHz bandwidth in less than 100 ns (scanning rate R exceeds 100 MHz/ns). In contrast to conventional quadratic microwave detectors, the output voltage of the STNO analyzer is proportional to the amplitude of the input microwave signal I_{\mathrm{ rf}} with sensitivity S = dV_{\mathrm{ dc}}/dI_{\mathrm{ rf}} \approx 750~\rm mV/mA$ . The minimum detectable signal of the analyzer depends on the scanning rate $R$ and, at low $R \approx 1~\rm MHz/ns$ , is about 1 pW. [ABSTRACT FROM AUTHOR]

A design of a magnonic phase shifter operating without an external bias magnetic field is proposed. The phase shifter uses a localized collective spin wave mode propagating along a domain wall "waveguide" in a dipolarly-coupled magnetic dot array with a chessboard antiferromagnetic (CAFM) ground state. It is demonstrated numerically that the remagnetization of a single magnetic dot adjacent to the domain wall waveguide introduces a controllable phase shift in the propagating spin wave mode without significant change to the mode amplitude. It is also demonstrated that a logic XOR gate can be realized in the same system. [ABSTRACT FROM AUTHOR]

Approximate electrodynamic boundary conditions are derived for an array of dipolarly coupled magnetic elements. It is assumed that the elements' thickness is small compared to the wavelength of an electromagnetic wave in a free space. The boundary conditions relate electric and magnetic fields existing at the top and bottom sides of the array through the averaged uniform dynamic magnetization of the array. This dynamic magnetization is determined by the collective dynamic eigen-excitations (spin wave modes) of the array and is found using the external magnetic susceptibility tensor. The problem of oblique scattering of a plane electromagnetic wave on the array is considered to illustrate the use of the derived boundary conditions. [ABSTRACT FROM AUTHOR]

The frequency spectrum of spin-wave edge modes localized near the boundaries of a finite array of dipolarly coupled magnetic nanopillars is calculated theoretically. Two mechanisms of edge mode formation are revealed: inhomogeneity of the internal static magnetic field existing near the array boundaries and time-reversal symmetry breaking of the dipole-dipole interaction. The latter mechanism is analogous to the formation mechanism of a surface Damon-Eschbach mode in continuous in-plane magnetized magnetic films and is responsible for the nonreciprocity of edge modes in finite-width nanopillar arrays. The number of edge modes in nanopillar arrays depends on the spatial profile of the internal static magnetic field near the array boundaries and several edge modes are formed if a substantial field inhomogeneity extends over several rows of nanopillars. [ABSTRACT FROM AUTHOR]

It is predicted that in 2D magnonic crystals the edge rotational magnons of forward volume magnetostatic spin waves can exist. Under certain conditions, locally bounded magnons may appear within the crystal consisting of the ferromagnetic matrix and periodically inserted magnetic/non-magnetic inclusions. It is also shown that interplay of different resonances in 2D magnonic crystal may provide conditions for spin wave modes existence with negative group velocity. [ABSTRACT FROM AUTHOR]

The strong strain-mediated magnetoelectric (ME) coupling found in thin-film ME heterostructures has attracted an ever-increasing interest and enables realization of a great number of integrated multiferroic devices, such as magnetometers, mechanical antennas, RF tunable inductors and filters. This paper first reviews the thin-film characterization techniques for both piezoelectric and magnetostrictive thin films, which are crucial in determining the strength of the ME coupling. After that, the most recent progress on various integrated multiferroic devices based on thin-film ME heterostructures are presented. In particular, rapid development of thin-film ME magnetometers has been seen over the past few years. These ultra-sensitive magnetometers exhibit extremely low limit of detection (sub-pT/Hz1/2) for low-frequency AC magnetic fields, making them potential candidates for applications of medical diagnostics. Other devices reviewed in this paper include acoustically actuated nanomechanical ME antennas with miniaturized size by 1–2 orders compared to the conventional antenna; integrated RF tunable inductors with a wide operation frequency range; integrated RF tunable bandpass filter with dual H- and E-field tunability. All these integrated multiferroic devices are compact, lightweight, power-efficient, and potentially integrable with current complementary metal oxide semiconductor (CMOS) technology, showing great promise for applications in future biomedical, wireless communication, and reconfigurable electronic systems. [ABSTRACT FROM AUTHOR]

The article focuses on a study which described giant nonreciprocity in transmitting surface acoustic waves on lithium niobate substrate coated with ferromagnet/insulator/ferromagnet multilayer structure. The structure is utilized with a unique asymmetric band diagram and expanded on magnetoelastic coupling theory to demonstrate how the magnetic bands couple with acoustic waves in a single direction. Results of the study are discussed. Materials and methods used are described.

The Bose-Einstein condensate of magnons (mBEC) that is formed at room temperature in parametrically pumped magnetic films is doubly degenerate: it is formed simultaneously in two spectral minima corresponding to the lowest-energy magnons propagating in opposite directions along the in-plane bias magnetic field. In this work the interactions of magnons in the mBEC are studied both theoretically and experimentally. It is shown by direct calculation that the magnons residing in each of the degenerate spectral minima of mBEC form a practically ideal magnon gas, as the attractive self-interaction between these magnons is very weak. At the same time, the interaction between the magnons residing in different spectral minima, corresponding to opposite directions of the magnon wave vector, is relatively strong and repulsive, leading to a repulsive total intermagnon interaction. By measuring the spectral characteristics of the mBEC it is shown that with increased magnon density the energy per magnon in the mBECs increases, thus confirming experimentally that the net intermagnon interaction in a doubly degenerate mBEC is repulsive. [ABSTRACT FROM AUTHOR]

The development of compact and tunable room temperature sources of coherent THz-frequency signals would open a way for numerous new applications. The existing approaches to THz-frequency generation based on superconductor Josephson junctions (JJ), free electron lasers, and quantum cascades require cryogenic temperatures or/and complex setups, preventing the miniaturization and wide use of these devices. We demonstrate theoretically that a bi-layer of a heavy metal (Pt) and a bi-axial antiferromagnetic (AFM) dielectric (NiO) can be a source of a coherent THz signal. A spin-current flowing from a DC-current-driven Pt layer and polarized along the hard AFM anisotropy axis excites a non-uniform in time precession of magnetizations sublattices in the AFM, due to the presence of a weak easy-plane AFM anisotropy. The frequency of the AFM oscillations varies in the range of 0.1-2.0 THz with the driving current in the Pt layer from 108 A/cm2 to 109 A/cm2. The THz-frequency signal from the AFM with the amplitude exceeding 1 V/cm is picked up by the inverse spin-Hall effect in Pt. The operation of a room-temperature AFM THz-frequency oscillator is similar to that of a cryogenic JJ oscillator, with the energy of the easy-plane magnetic anisotropy playing the role of the Josephson energy. [ABSTRACT FROM AUTHOR]

It is demonstrated theoretically that a thin layer of an anisotropic antiferromagnetic (AFM) insulator can effectively conduct spin current through the excitation of a pair of evanescent AFM spin wave modes. The spin current flowing through the AFM is not conserved due to the interaction between the excited AFM modes and the AFM lattice and, depending on the excitation conditions, can be either attenuated or enhanced. When the phase difference between the excited evanescent modes is close to π/2, there is an optimum AFM thickness for which the output spin current reaches a maximum, which can significantly exceed the magnitude of the input spin current. The spin current transfer through the AFM depends on the ambient temperature and increases substantially when temperature approaches the Néel temperature of the AFM layer. [ABSTRACT FROM AUTHOR]

A general theory of collective spin-wave edge modes in semi-infinite and finite periodic arrays of magnetic nanodots having uniform dynamic magnetization (macrospin approximation) is developed. The theory is formulated using a formalism of multivectors of magnetization dynamics, which allows one to study edge modes in arrays having arbitrarily complex primitive cells and lattice structure. The developed formalism can describe spin-wave edge modes localized both at the physical edges of the array and at the internal "domain walls" separating the array regions existing in different static magnetization states. Using a perturbation theory, in the framework of the developed formalism, it is possible to calculate damping of the edge modes and to describe their excitation by external variable magnetic fields. The theory is illustrated on the following practically important examples: (i) calculation of the FMR absorption in a finite nanodot array having the shape of a right triangle; (ii) calculation of the spectra of nonreciprocal spin-wave edge modes, including the modes at the physical edges of an array and modes at the domain walls inside the array; and (iii) study of the influence of the domain wall modes on the FMR spectrum of an array existing in a nonideal chessboard antiferromagnetic ground state. [ABSTRACT FROM AUTHOR]