Equilibrium and nonequilibrium solitons in a lossy split-step system with lumped amplification

We propose a more realistic version of the recently introduced split-step model (SSM), which consists of periodically alternating dispersive and nonlinear segments, by adding uniformly distributed loss and lumped gain to it. In the case when the loss is exactly balanced by gain, a family of stable equilibrium solitons (ESs) is found. Unless the system's period L is very small, saturation is observed in the dependence of the amplitude of the established ES vs. that of the initial pulse. Stable nonequilibrium solitons (NESs) are found in the case when the gain slightly exceeds (by up to 3%) the value necessary to balance the loss. The existence of NESs is possible as the excessive energy pump is offset by permanent radiation loss, which is confirmed by computation of the corresponding Poynting vector. Unlike ESs that form a continuous family of solutions, NES is an isolated solution, which disappears in the limit of small L, i.e., it cannot be found in the overpumped nonlinear Schroedinger equation. Interactions between ESs turn out to be essentially the same as in SSM without loss and gain, while interactions between NESs are different: two NESs perturb each other by the radiation jets emanating from them, even if they are separated by a large distance. Moving NESs survive collisions, changing their velocities.Comment: a latex text file and seven jpg figure files. Physics Letter A, in pres

Detection of spin waves in permalloy using planar Hall effect

Rectification of microwave oscillations of magnetization in a permalloy film is realized using planar Hall effect. Two different rectified signals are obtained: a signal from the linearly excited uniform magnetization precession at the frequency of the external pumping and a signal from the pairs of contra-propagating short-wavelength spin waves parametrically generated at a half of the pumping frequency. The second, most unusual, rectified signal is caused by the uniform component of the dynamic magnetization created due to the interference of the phase correlated pairs of parametric spin waves

Supercurrent in a room temperature Bose-Einstein magnon condensate

We report evidence for the existence of a supercurrent of magnons in a magnon Bose-Einstein condensate prepared in a room temperature yttrium-iron-garnet magnetic film and subject to a thermal gradient. The magnon condensate is formed in a parametrically populated magnon gas, and its temporal evolution is studied by time-, frequency- and wavector-resolved Brillouin light scattering spectroscopy. It has been found that local heating in the focal point of a probing laser beam enhances the temporal decrease in the density of the freely evolving magnon condensate after the termination of the pumping pulse, but it does not alter the relaxation dynamics of the gaseous magnon phase. This phenomenon is understood as the appearance of a magnon supercurrent within the condensate due to a temperature- and, consequently, magnetisation-gradient induced phase gradient in the condensate wave function

Non-resonant wave front reversal of spin waves used for microwave signal processing

It is demonstrated that non-resonant wave front reversal (WFR) of spin-wave pulses caused by pulsed parametric pumping can be effectively used for microwave signal processing. When the frequency band of signal amplification by pumping is narrower than the spectral width of the signal, the non-resonant WFR can be used for the analysis of the signal spectrum. In the opposite case the non-resonant WFR can be used for active (with amplification) filtering of the input signal.Comment: 4 pages, 3 figure

Magnon-phonon coupling unmasked: a direct measurement of magnon temperature

Thermoelectric phenomena in magnetic materials present tantalizing possibilities for manipulating spin-information using heat in future 'spin caloritronic' devices. Key to unraveling their underlying physics is to understand spin-lattice interactions, i.e. the coupling between magnons (the quanta of magnetization excitations) and phonons (the quanta of lattice vibrations). Here, we present the first measurements of the spatial distribution of magnon temperature in a magnetic system subject to a lateral thermal (i.e. phonon temperature) gradient and demonstrate that, contrary to currently accepted theory, the magnon and phonon temperatures do not differ. This result has profound implications. In particular, it re-opens the question of how the spin Seebeck effect-which allows spin currents to be produced from thermal gradients, and is arguably the most intriguing and technologically relevant thermoelectric phenomenon of all-can exist, and which physics underpins it. Specifically, it reveals that if the general framework of the current theory of the effect holds, we must adopt a new concept of spectrally non-uniform magnon temperature.Comment: 13 pages, 4 figure

Noise properties of a resonance-type spin-torque microwave detector

We analyze performance of a resonance-type spin-torque microwave detector (STMD) in the presence of noise and reveal two distinct regimes of STMD operation. In the first (high-frequency) regime the minimum detectable microwave power $P_{\rm min}$ is limited by the low-frequency Johnson-Nyquist noise and the signal-to-noise ratio (SNR) of STMD is proportional to the input microwave power $P_{\rm RF}$. In the second (low-frequency) regime $P_{\rm min}$ is limited by the magnetic noise, and the SNR is proportional to $\sqrt{P_{\rm RF}}$. The developed formalism can be used for the optimization of the practical noise-handling parameters of a STMD.Comment: 3 pages, 2 figure

Monitoring Of Air Quality Parameters For Construction Of Fire Risk Detection Systems

The analysis of fire developmental process is given, which showed that there are seven stages of fire development, a set of phenomena (factors, signs) of fire risk condition, characterized by a set of defined parameters, corresponds to each stage. Observed that the registration of high staging factors (high ambient temperature, content of CO[2], etc.) means the registration of actual low staging fire (thermal destruction of materials gases, fumes, etc.) - fire risk situation. It is shown that the decrease of registered factor staging leads to construction of fire preventive and diagnostic systems as the lower is registered stage, the more uncertain is connection between the fact of its detection and a fire. It is indicated that with development of electronic equipment the staging of fire situations factors used for detection is reducing in whole, and also it is noted that for each control object it is necessary to choose (identify) the optimal factor, in particular, in many ways the optimal factor for aircrafts are smokes and their TV image

Magnonics: Experiment to Prove the Concept

An experimental scheme for studying spin wave propagation across thin film samples is proposed. An experiment upon a periodically layered nanowire is numerically simulated, while the sample might equally well be a continuous film or an array of elements (e.g. nanowires) that either have uniform composition or are periodically layered as in a magnonic crystal. The experiments could be extended to study domain wall induced spin wave phase shifts, and used for creation of the spin wave magnetic logic devices.Comment: Presented as a poster HP-09 at 50th MMM conference, San Jose, CA (Oct 30 - Nov3, 2005