Microscopic magnetic structuring of a spin-wave waveguide by ion implantation in a Ni81Fe19 layer

Abstract

We investigate the spin-wave excitation in microscopic waveguides fabricated by localized Cr + ion implantation in a ferromagnetic Ni 81 Fe 19 film. We demonstrate that spin-wave waveguides can be conveniently made by this technique. The magnetic patterning technique yields an increased damping and a reduction in saturation magnetization in the implanted regions that can be extracted from Brillouin light scattering measurements of the spin-wave excitation spectra. Furthermore, the waveguide performance as well as the internal field of the waveguide depend on the doping fluence. The results prove that localized ion implantation is a powerful tool for the patterning of magnon spintronic devices.The field of spin dynamics and spintronics has greatly benefited from micro-and nanopatterning techniques. The advancement of research on small magnetic structures 1-4 strongly depends on the possibility to fabricate structures of accurate sizes and shapes. Based on these developments, the focus of many investigation has turned to the realization of spin logic devices, which use the electron spin 5 or spin waves as information carrier. [6][7][8] In order to establish a pure spin-wave logic architecture, there is a need for spin-wave conduits for the transport of spin information between the individual logic devices. Thus, the fabrication and investigation of spinwave waveguides 9-12 has become a major research topic in the field of magnon spintronics. Currently, spin-wave waveguides with nanometer thicknesses and widths of several micrometers are fabricated by topographically patterning thin magnetic stripes onto a substrate that is usually nonmagnetic. However, the potential of other waveguide fabrication techniques have not been explored up to now, although they might contribute to an improvement of waveguide properties that were not accessible so far, such as, e.g., the inhomogeneity of the internal magnetic field. 13 In that respect, ion implantation of ferromagnetic films is a promising technique for the fabrication of thin films with microscopic magnetic substructures. [14][15][16] The different components contributing to the change in the magnetic properties due to Cr + ion implantation in Ni 81 Fe 19 films have been thoroughly investigated. 17 In this letter a purely magnetic microscopic structuring of spin-wave waveguides by localized ion implantation in a Ni 81 Fe 19 film is presented. We have designed a stripe shaped area with unchanged magnetic properties, embedded in a film with a reduced saturation magnetization M S and an increased damping α. It is shown that the spinwave distribution within the stripe has similar proper-FIG. 1. (Color online) Schematic sample setup. A Ni81Fe19 film with a thickness of 20 nm is grown on top of a Si/SiO2 substrate. By localized implantation of Cr + ions the magnetic properties of the implanted parts of the film are changed while a shielded region yields a 2 µm wide Ni81Fe19 stripe with unchanged properties embedded in the film. A subsequently produced Cu microwave antenna serve...

Realization of a spin-wave multiplexer

“…Furthermore, the same approach can be adapted to ferromagnetic insulators, such as yttrium iron garnets, where the damping of the magnetization dynamics is greatly reduced and therefore the spin-wave propagation distance is significantly increased. Another approach to reduce the currents required to magnetize the spin-wave waveguide perpendicular to the transport direction is to use ion implantation to imprint waveguides into paramagnetic or ferromagnetic films 24,25 . In such waveguides the shape anisotropy is strongly reduced due to the surrounding ferro-or paramagnetic environment.…”

Micro-focused Brillouin light scattering: imaging spin waves at the nanoscale

“…In this study the implantation of Cr + ions was used to achieve a periodic modulation of the saturation magnetization in a Ni 81 Fe 19 stripe without actually changing the topography, i.e., without altering the thickness of the magnetic material [89,90]. In a magnonic crystal the chosen periodicity-1 µm in the actual case-defines the Bragg condition and, thus, the position of the resulting band gaps in terms of the wave vector.…”

Optically reconfigurable magnetic materials

“…The spin-wave dispersion relation depends on many parameters, such as the geometry of the spin-wave waveguide (film thickness and waveguide width), external magnetic field H ext , and saturation magnetization M S . In fact, all of these parameters have already been used to fabricate magnonic crystals [6][7][8]12,13,[18][19][20] : arrays of metallic stripes, etched grooves or antidots, biasing magnetic field or periodic variation of the saturation magnetization using ion implantation.However, all available methods for the fabrication of such spintronic devices result in spatially constant magnetic materials. J. Topp et al have shown that the parameters of magnetic materials can be changed locally after the rather time-consuming fabrication of the spintronic device 21 -but the functionality of the device stays the same.…”

“…Structuring has been used to control mechanical 10 , optical 11 , and even magnetic properties 12,13 . Periodic variation of the magnetic material's parameters allows the realization of magnonic crystals with novel properties not found in the unstructured material.…”