Explore the vast range of titles available.

The origin of unusual anisotropic electronic properties in the spin-density wave state of iron pnictides has conventionally been attributed to the breaking of four-fold rotational symmetry associated with the collinear magnetic order. By using a minimal two-orbital model, we show that a significant portion of the contribution to the anisotropy may come from the Dirac cones, which are not far away from the Fermi level. We demonstrate this phenomenon by examining optical conductivity and quasiparticle interference in the Dirac-semimetallic state with spin-density wave order, and the latter can be obtained by choosing appropriate interaction parameters and orbital splitting between the d xz and d yz orbitals. We further extend this study to investigate the low-energy spin-wave excitations in the Dirac-semimetallic state with spin-density wave order.

Frustrated spin systems have been first investigated five decades ago. Well-known examples include the Ising model on the antiferromagnetic triangular lattice studied by G H Wannier in 1950 and the Heisenberg helical structure discovered independently by A Yoshimori, J Villain and T A Kaplan in 1959. However, many properties of frustrated systems are still not well understood at present. Recent studies reveal that established theories, numerical simulations as well as experimental techniques have encountered many difficulties in dealing with frustrated systems. This volume highlights the latest theoretical, numerical and experimental developments in the field. The book is intended for post-graduate students as well as researchers in statistical physics, magnetism, materials science and various domains where real systems can be described with the spin language. Explicit demonstrations of formulae and full arguments leading to important results are given.

We consider the spin wave resonances (SWRs) magnetoelastic excitation and electric detection in a hybrid bulk acoustic wave resonator containing YIG/Pt bilayer. The influence of micrometer and submicrometer yttrium iron garnet (YIG) film thickness on the efficiency of SWR excitation accompanied by a spin pumping from YIG to Pt has been theoretically studied. The frequency and thickness dependencies of inverse spin Hall effect (ISHE) voltage and microwave reflection coefficient are analytically and numerically investigated and discussed. Due to the non-uniform effective magnetic field of elastic nature, the higher SWR modes (both even and odd) can be excited with an efficiency comparable to the efficiency of the fundamental mode at the ferromagnetic resonance frequency. If an integer number of acoustic half-waves fits into the YIG film thickness, forbidden zones arise in the SWR spectrum: at certain thickness values, only even or only odd SWR modes are excited.

In this work, we investigate the structural and dynamic magnetic properties of yttrium iron garnet (YIG) films grown onto gadolinium gallium garnet (GGG) substrates with thin platinum, iridium, and gold spacer layers. Separation of the YIG film from the GGG substrate by a metal film strongly affects the crystalline structure of YIG and its magnetic damping. Despite the presence of structural defects, however, the YIG films exhibit a clear ferromagnetic resonance response. The ability to tune the magnetic damping without substantial changes to magnetization offers attractive prospects for the design of complex spin-wave conduits. We show that the insertion of a 1-nm-thick metal layer between YIG and GGG already increases the effective damping parameter enough to efficiently absorb spin waves. This bilayer structure can therefore be utilized for magnonic waveguide termination. Investigating the dispersionless propagation of spin-wave packets, we demonstrate that a damping unit consisting of the YIG/metal bilayers can dissipate incident spin-wave signals with reflection coefficient R < 0.1 at a distance comparable to the spatial width of the wave packet.

Spin-wave devices are regarded as one of the most promising candidates for future computation and data processing. How to manipulate spin-wave propagation is a key issue in realizing the functionality of these of devices. The existing manipulation methods have serious drawbacks for constructing practical spin-wave devices. Here, we propose an approach to harness the amplitude and mode excitation of traveling spin waves by introducing unique micromagnetic textures in a permalloy waveguide directly exchange-coupled to a pair of cobalt nanomagnets. We demonstrate that the imprinted micromagnetic textures, i.e., the 360° domain wall and magnetic buckle, which play different roles in spin-wave manipulation, can be interchanged with each other repeatedly by using a sequence of homogeneous magnetic fields. Moreover, the suggested architecture could easily be tailored to implement fundamental logic-NOT operation. In light of the internal-field profile of the micromagnetic textures, speculation is offered concerning the physical origin underlying the observed spin-wave modulation phenomena.

Spin wave propagation is studied through a diffraction grating in a 200 nm thick YIG film by using scanning time resolved magneto‐optic Kerr microscopy (TR‐MOKE) and supported by micromagnetic simulations. Caustic‐like spin wave emission and the hybridization of Damon Eshbach (DE) type spin wave modes within the grating region, depending on the magnetic field and the dimensions of the grating, are observed. Hybridization leads to an increased attenuation length for propagating spin waves and consequently to a transmission stop‐band for spin waves at the grating for a certain magnetic field range. A simple design of a diffraction grating can act as a spin wave stop band for spin waves in the Damon Eshbach geometry if the total internal field is shifted to a value where hybridization between the Damon Eshbach mode and a standing spin wave mode occurs.

Spin waves (SWs), being usually reflected by domain walls (DWs), could also be channeled along them. Edge SWs yield the interesting, and potentially applicable to real devices property of broadband spin wave confinement to the edges of the structure. Here, we investigate through numerical simulations the propagation of quasi one-dimensional spin waves in triangle-shaped amorphous YIG (Y 3 Fe 5 O 12 ) micron sized ferromagnets as a function of the angle aperture. The edge spin waves (ESWs) have been propagated over the corner in triangles of 2 microns side with a fixed thickness of 85 nm. Parameters such as superior vertex angle (in the range of 40 ∘ –75 ∘ ) and applied magnetic field have been optimized in order to obtain a higher transmission coefficient of the ESWs over the triangle vertex. We observed that for a certain aperture angle for which dominated ESW frequency coincides with one of the localized DW modes, the transmission is maximized near one and the phase shift drops to π / 2 indicating resonant transmission of ESWs through the upper corner. We compare the obtained results with existing theoretical models. These results could contribute to the development of novel basic elements for spin wave computing. Article Highlights High transmission of edge spin waves through a vertex domain wall in triangular dots. Dependence in the propagation on the local topology of the vertex domain wall. Resonant interaction between the bulk and the local domain wall spin wave modes in the magnetic nanostructure.

The microwave properties of structures in the form of the 2 μm iron-yttrium garnet (YIG) films, grown by the ion beam sputtering deposition method on epitaxially mismatched substrates of ferroelectric ceramics based on lead zirconate titanate (PZT, PbZr0.45Ti0.55O3), are discussed. The obtained structures were formed and pre-smoothed by the ion beam planarization substrates with the use of an anti-diffusion layer of titanium dioxide TiO2. The atomic force microscopy showed that the planarization of the substrates allows for reaching a nanoscale level of roughness (up to 10 nm). The presence of smooth plane–parallel interfaces of YIG/TiO2 and TiO2/PZT is evidenced by scanning electron microscopy performed in focused gallium ion beams. Ferromagnetic resonance spectroscopy revealed a broadening in the absorption line of the ferrite garnet layers in the resonance ≈ 100 Oe. This broadening is associated with the presence of defects caused by the of the ceramic substrate non-ideality. The estimated damping coefficient of spin waves turned out to be ~10−3, which is two orders of magnitude higher than in an ideal YIG single crystal. The YIG/TiO2/PZT structures obtained can be used for the study of spin waves.

The Swendsen-Wang dynamics is a Markov chain widely used by physicists to sample from the Boltzmann-Gibbs distribution of the Ising model. Cooper, Dyer, Frieze and Rue proved that on the complete graph K_n the mixing time of the chain is at most O(\\sqrt{n}) for all non-critical temperatures. In this paper the authors show that the mixing time is \\Theta(1) in high temperatures, \\Theta(\\log n) in low temperatures and \\Theta(n^{1/4}) at criticality. They also provide an upper bound of O(\\log n) for Swendsen-Wang dynamics for the q-state ferromagnetic Potts model on any tree of n vertices.