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A magnon parametron is a calculating element that carries binary information by a discretized oscillating phase: 0 and π. Owing to the strong non-linearity of the magnetization dynamics, the oscillation phase flips to another stochastically, which can give a rise to unconventional computing functionalities, including probabilistic computing. Here, we investigated the stochastic dynamics of ferromagnetic-metal magnon parametron, of which the precession phase is discretized into two (0 and π) by parametric pumping of magnons. We found that an AC magnetic field perpendicular to an external field can control the precession phase in the magnon parametron, of which amplitude dependence follows the sigmoid function, a requirement for probabilistic bit operation. We also found that the time scale for flipping between different precession phases grows exponentially as pumping microwave power. Our finding ensures that the magnon parametron can be used as a calculating element for unconventional computing schemes based on bistable systems. [ABSTRACT FROM AUTHOR]

The Peltier effect, discovered in 1834, converts a charge current into a heat current in a conductor, and its performance is described by the Peltier coefficient, which is defined as the ratio of the generated heat current to the applied charge current.sup.1,2. To exploit the Peltier effect for thermoelectric cooling or heating, junctions of two conductors with different Peltier coefficients have been believed to be indispensable. Here we challenge this conventional wisdom by demonstrating Peltier cooling and heating in a single material without junctions. This is realized through an anisotropic magneto-Peltier effect in which the Peltier coefficient depends on the angle between the directions of a charge current and magnetization in a ferromagnet. By using active thermography techniques.sup.3-10, we observe the temperature change induced by this effect in a plain nickel slab. We find that the thermoelectric properties of the ferromagnet can be redesigned simply by changing the configurations of the charge current and magnetization, for instance, by shaping the ferromagnet so that the current must flow around a curve. Our experimental results demonstrate the suitability of nickel for the anisotropic magneto-Peltier effect and the importance of spin-orbit interaction in its mechanism. The anisotropic magneto-Peltier effect observed here is the missing thermoelectric phenomenon in ferromagnetic materials--the Onsager reciprocal of the anisotropic magneto-Seebeck effect previously observed in ferromagnets--and its simplicity might prove useful in developing thermal management technologies for electronic and spintronic devices.A 'magneto-Peltier effect' produces cooling or heating in a material without junctions, by forcing a change in angle between the current and magnetization in a single ferromagnetic nickel slab., Author(s): Ken-ichi Uchida [sup.1] [sup.2] [sup.3] [sup.4] , Shunsuke Daimon [sup.4] [sup.5] [sup.7] , Ryo Iguchi [sup.1] , Eiji Saitoh [sup.3] [sup.4] [sup.5] [sup.6] [sup.7] Author Affiliations:(1) National Institute for [...]

In-plane standing spin-wave modes in a minute magnetic disk are directly observed by using time-resolved magneto-optical microscopy synchronized with microwaves. The time-resolved microscopy allowed us to obtain snapshots of standing spin-wave modes in a magnetic disk, which show a hourglass-like standing spin wave pattern. We found that the characteristic pattern is caused by spatially nonuniform magnetization and a strong microwave excitation in terms of finite element calculation and micromagnetic simulations. The technique we developed in this work allows us to access magnetization dynamics in microstructured magnets under strong microwave pumping. [ABSTRACT FROM AUTHOR]

Spin-driven thermoelectric (STE) generation based on the combination of the spin Seebeck effect (SSE) and inverse spin Hall effect is an alternative to conventional semiconductor-based thermocouples as it is large scale, low cost, and environment-friendly. The STE device is thought to be radiation hard, making it attractive for space and nuclear technology applications. By using magnetometry, transmission electron microscopy, and the hard X-ray photoemission spectroscopy (HAXPES) measurements, we show that an STE device made of single-crystalline Y3Fe5O12 (YIG)/Pt heterostructures has tolerance to irradiation of high-energy heavy ion beams. We used 200 MeV gold ion beams modeling cumulative damages due to fission products emitted from the surface of spent nuclear fuels. By varying the dose level, we confirmed that the thermoelectric and magnetic properties of the single-crystalline YIG/Pt STE device are finite at the ion-irradiation dose up to 1012 ions/cm2 fluence. In addition, the HAXPES measurements were performed to understand the effects at the interface of YIG/Pt. The HAXPES data suggest that the chemical reaction regarding Fe and O that diminishes the SSE signals is promoted with the increase of the irradiation dose. The understandings of the damage analysis in YIG/Pt are beneficial for developing better STE devices applicable to harsh environmental usages. [ABSTRACT FROM AUTHOR]

Magnetization dynamics induced by parametric pumping has been investigated by numerically calculating a master equation. The results show that a weak microwave with the same frequency as the ferromagnetic resonance, a bias microwave, can be used to control which phase state appears under a parametric excitation. The amplitude dependence of the appearance probability exhibits sigmoid-like behavior. We have also found that a strong microwave causes an amplitude squeezed state with a sub-Poissonian distribution, which has a potential to serve as a quantum information resource. [ABSTRACT FROM AUTHOR]

Magnetization dynamics induced by parametric excitation in a magnetic dot has been investigated by using ac spin pumping and inverse spin-Hall effects. An Ising-like pair of states with different precession phases was found to be stabilized in a controllable way under the excitation. The result shows that the dot can be used as a parametron-bit carrier. Upon increasing the excitation power, stochastic transition between the states was observed, and the occurrence probability of each state can be tuned by means of additional microwaves, opening an application to probabilistic bit operation. [ABSTRACT FROM AUTHOR]

In superconductors, a topological configuration of the superconducting order parameter called a superconducting vortex carries magnetization. Such a magnetic topological object behaves like a minute particle generating a magnetic flux. Since the flux is localized with a nanometer scale, the vortex provides a nano-scale probe for local magnetic fields. Here we show that information of magnetic stripes in insulators can be read out by using vortices in an adjacent superconductor film as a probe. The orientation and width of magnetic micro stripes are both transcribed into resistance change of the superconductor through the modulation of vortex mobility affected by local magnetization. By changing the direction of external magnetic fields, zero-field resistance changes continuously according to the stripe orientation, and its modulation magnitude reaches up to 100%. The width of the stripes can also be estimated from the oscillatory magnetoresistance. Our results demonstrate a new possibility for non-volatile analog memory devices based on topological objects. [ABSTRACT FROM AUTHOR]

For longitudinal spin Seebeck effect (LSSE) devices, a multilayer structure comprising ferromagnetic and nonmagnetic layers is expected to improve their thermoelectric power. In this study, we developed a fabrication method for alternately stacked yttrium–iron–garnet (YIG)/Pt multilayer films on a gadolinium gallium garnet (GGG) (110) substrate, GGG/[YIG(49 nm)/Pt(4 nm)]n (n = 1–5) based on room-temperature sputtering and ex-situ post-annealing methods and we evaluated their structural and LSSE properties. The fabricated [YIG/Pt]n samples show flat YIG/Pt interfaces and almost identical saturation magnetization Ms although they contain polycrystalline YIG layers on Pt layers as well as single-crystalline YIG layers on GGG. In the samples, we observed clear LSSE signals and found that the LSSE thermoelectric power factor (PF) increases monotonically with increasing n; the PF of the [YIG/Pt]5 sample is enhanced by a factor of ∼28 compared to that of [YIG/Pt]1. This work may provide a guideline for developing future multilayer-based LSSE devices. [ABSTRACT FROM AUTHOR]

The frequency dependence of magnetization precession in spin pumping has been investigated using the inverse spin-Hall effect in a Pt/Y3Fe5O12 bilayer film. We found that the magnitude of a spin current generated by the spin pumping depends weakly on the applied microwave frequency. This weak dependence, which is attributed to the compensation between the frequency change in the spin-pumping cycle and the dynamic magnetic susceptibility, is favorable for making a spin-current-driven microwave demodulator. This behavior is consistent with a model calculation based on the Landau-Lifshitz-Gilbert equation combined with the spin mixing. [ABSTRACT FROM AUTHOR]

Mechanical resonance properties of a microcantilever made of a magnetic insulator have been investigated by laser-doppler vibrometry under DC magnetic fields and microwaves. At ferromagnetic resonance conditions, reduction of magnetization along the DC field was detected as a change in the mechanical resonance frequency. Above a microwave power threshold at which the change in the mechanical resonance frequency deviates from the linear dependence on the power, the mechanical damping was found to be enhanced steeply. The result suggests that the non-linear magnetization dynamics gives rise to additional dissipation in the mechanical motion. [ABSTRACT FROM AUTHOR]

We propose a dual gravitational theory corresponding to isotropic ferromagnetic systems based on the holographic duality, and establish the holographic dictionary between physical quantities in ferromagnets and the gravitational theory. Utilizing the holographic dictionary, the holographic calculation in the dual gravitational theory is shown to reproduce thermodynamics of ferromagnets including ferromagnetic phase transitions and low-temperature behaviors originating from magnons and conduction electrons. We further derive the equation for magnetization dynamics in ferromagnets from the equations for scalar fields and non-abelian gauge fields on charged black holes in the dual gravitational theory. From these results, the holographic duality is expected to give a new guiding principle to explore new phenomena in spintronics and magnonics based on the gravitational perspective. • Dual gravitational theory for ferromagnetic systems based on holographic duality. • Ferromagnetic Phase transition and magnons in dual gravitational theory. • Spin-wave equation from non-abelian gauge field in dual gravitational theory. [ABSTRACT FROM AUTHOR]

A magnetic domain wall (DW) is a spatially localized change of magnetization configuration in a magnet. This topological object has been predicted to behave at low energy as a composite particle with finite mass. This particle will couple directly with electric currents as well as magnetic fields, and its manipulation using electric currents is of particular interest with regard to the development of high-density magnetic memories. The DW mass sets the ultimate operation speed of these devices, but has yet to be determined experimentally. Here we report the direct observation of the dynamics of a single DW in a ferromagnetic nanowire, which demonstrates that such a topological particle has a very small but finite mass of 6.6×10-23?kg. This measurement was realized by preparing a tunable DW potential in the nanowire, and detecting the resonance motion of the DW induced by an oscillating current. The resonance also allows low-current operation, which is crucial in device applications; a DW displacement of 10?µm was induced by a current density of 1010?A?m-2. [ABSTRACT FROM AUTHOR]

The inverse spin-Hall effect (ISHE), conversion of spin currents into electric voltage, was observed in Ni81Fe19/N (N=Pt, Pd, Ag, and Au) films using the spin pumping at room temperature. The spin pumping driven by magnetization precession in the Ni81Fe19 layer injects a spin current into the layer, giving rise to an electric potential difference between the edges of the layer via ISHE.We found resonant electromotive force signals at the ferromagnetic resonance condition in the Ni81Fe19/N films. The spectral shape of the electromotive force signals are well reproduced by simple Lorentz functions, which is consistent with the prediction of ISHE induced by the spin pumping. The ISHE signal was observed to typically be enhanced in the Ni81Fe19/Pt system, showing the crucial role of the spin-orbit interaction in ISHE induced by the spin pumping. [ABSTRACT FROM AUTHOR]

The article provides information related to magnetism. The author relates that a magnet consists of atomic scale magnets called spins. If a strong magnetic field is applied to a fixed magnet, the spins rotate to align with the field. As a result, the magnetization in the magnet takes on the direction of the applied magnetic field. On the other hand, physicists have come up with an innovative way of manipulating the direction of magnetization in a solid. The approach might be used to make low-power consumption computer memory devices.

We theoretically investigate the spin Seebeck effect (SSE) in antiferromagnets and ferrimagnets, and show that the SSE vanishes in antiferromagnets but survives in ferrimagnets even at the magnetization compensation point despite the absence of its saturation magnetization. The nonvanishing SSE in ferrimagnets stems from two nondegenerate magnons. We demonstrate that the magnitude of the SSE in ferrimagnets is unchanged across the magnetization compensation point. [ABSTRACT FROM AUTHOR]

We present a theory of the spin Hall magnetoresistance (SMR) in multilayers made from an insulating ferromagnet F, such as yttrium iron garnet (YIG), and a normal metal N with spin-orbit interactions, such as platinum (Pt). The SMR is induced by the simultaneous action of spin Hall and inverse spin Hall effects and therefore a nonequilibrium proximity phenomenon. We compute the SMR in F∣N and F∣N∣F layered systems, treating N by spin-diffusion theory with quantum mechanical boundary conditions at the interfaces in terms of the spin-mixing conductance. Our results explain the experimentally observed spin Hall magnetoresistance in N∣F bilayers. For F∣N∣F spin valves we predict an enhanced SMR amplitude when magnetizations are collinear. The SMR and the spin-transfer torques in these trilayers can be controlled by the magnetic configuration. [ABSTRACT FROM AUTHOR]