The half antivortex, a fundamental topological structure which determines magnetization reversal of submicron magnetic devices with domain walls, has been suggested also to play a crucial role in spin torque induced vortex core reversal in circular disks. Here we report on magnetization reversal in circular disks with nanoholes through consecutive metastable states with half antivortices. Inplane anisotropic magnetoresistance and broadband susceptibility measurements accompanied by micromagnetic simulations reveal that cobalt (Co) disks with two and three linearly arranged nanoholes directed at 45º and 135º degrees (º) with respect to the external magnetic field show reproducible step-like changes in the anisotropic magnetoresistance and magnetic permeability due to transitions between different intermediate states mediated by vortices and half antivortices confined to the dot nanoholes and edges, respectively. Our findings are relevant for the development of multi-hole based spintronic and magnetic memory devices.(*) Corresponding author: farkhad.aliev@uam.es

We report on room temperature low frequency noise due to magnetic

Broadband magnetization response of equilateral triangular 1000 nm Permalloy dots has been studied under an in-plane magnetic field, applied parallel (buckle state), and perpendicular (Y state) to the triangles base. Micromagnetic simulations identify edge spin waves (E-SWs) in the buckle state as SWs propagating along the two adjacent edges. These quasi one-dimensional spin waves emitted by the vertex magnetic charges gradually transform from propagating to standing due to interference and are weakly affected by dipolar interdot interaction and variation of the aspect ratio. The possibility to excite and manipulate spin waves (SWs) by magnetic fields or electric currents has opened perspectives for their implementation in communication and information processing and storage technologies. [1][2][3][4] Engineering of propagating of standing SWs in magnetic elements, as well as SW excitation and propagation in long strips or other two dimensional magnetic structures, [3][4][5] has been a subject of recent intensive applied and fundamental research. Magnetic stripes with spin waves travelling inside are currently basic elements of magnonic waveguides. 3,4Very recent studies predict however the possibility of excitation and propagation of a different kind of SW modes, so called edge spin waves (E-SWs) in individual twodimensional magnetic structures 6,7 and extended magnonic crystals. 8,9 It has been suggested that the E-SWs are capable of providing new functionalities to spintronic and magnonic devices. These features include an easy modulation of SW spectra by mechanical structuring of the boundaries of the waveguide, 6 unidirectional SW propagation, easily channelization, twisting, splitting, and manipulation, in a magnetic field perpendicular to the plane. 8,9 Spin waves have recently been reported to propagate along the long strip edges with inhomogeneous magnetization 10 when excited by a perpendicular extended antenna. However, these spin waves were found to spread over the strip at high frequencies transforming into two-dimensional and losing therefore the edge character.10 Observations of the E-SWs truly linked with the magnetically inhomogeneous edge states remain unclear.Here, we present experimental evidence of excitation and detection of quasi one-dimensional edge SWs emitted by the vertex magnetic charges of magnetic triangular dots. We observed that the edge SWs gradually transform from propagating to standing due to interference and are weakly affected by the variation of the dot aspect ratio. In order to effectively excite the spin waves locally, one needs either to apply a strongly nonhomogenous local microwave field (which, for example, could be tailored by a spin torque oscillator or small antenna [11][12][13][14] ) or by a quasi homogeneous microwave field interacting with nohomogeneous local magnetization. 15 In our triangular dots, the vertices are natural sources of strong local magnetic charges. The application of an in-plane magnetic field parallel to the triangles base, resulting in the bu...

We explore the dynamics of spiral spin waves in Permalloy nano-elements with variable aspect ratio of geometric dimensions, and their potential use as improved spin wave emitters with no or little biasing field required. Numerical results show that above a certain thickness, propagating spiral waves can be obtained in circular and square shaped elements in a flux closure state. VNA-FMR experiments on 20 nm (thin) and 80 nm (thick) samples confirm two type of spectra corresponding to different dispersions for thinner and thicker elements. We show that, for the thicker films, the vortex core region acts as a source of large amplitude spiral spin waves, which dominate over other modes. In case of the thinner elements, these modes are critically damped. For different shapes of the patch, we show that a rich collection of confined propagating modes can also be excited, modifying the final wave front and enriching the potential of the nano-dot as a spin wave emitter. We give an explanation for the intense spiral modes from the perspective of a balance of dipolar and exchange energies in the sample. arXiv:2001.09053v1 [cond-mat.mes-hall]

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