Zero-field propagation of spin waves in waveguides prepared by focused ion beam direct writing

Abstract

Metastable Fe78Ni22 thin films are excellent candidates for focused ion beam direct writing of magnonic structures due to their favorable magnetic properties. The focused ion beam transforms the originally nonmagnetic fcc phase into the ferromagnetic bcc phase with an additional control over the direction of uniaxial magnetic in-plane anisotropy and the saturation magnetization. The induced anisotropy allows to stabilize transverse direction of magnetization in narrow waveguides. Therefore, it is possible to propagate spin waves in these waveguides in the favorable Demon-Eshbach geometry without the presence of any external magnetic field. Nowadays, the vibrant field of magnonics stands on the edge between development of elementary building blocks of magnonic circuitry and envisioned all magnon on-chip devices [1,2]. The magnonic devices, utilizing physics of spin waves, are recognized to have potential in information processing in the frequency range from gigahertz to terahertz. High frequencies, together with low energy of elementary excitations render the magnonic devices suitable for beyond-CMOS computational technologies. Many concepts of future devices used for steering and manipulating spin waves have been presented recently [3][4][5][6]. To allow further advances in this field, new types of materials possessing additional means of control over their magnetic properties together with good spin wave propagation are needed.Here we show, that magnonic waveguides allowing for fast spin-wave propagation at zero magnetic field can be directly written into metastable Fe78Ni22 thin films by focused ion beam (FIB). The local dose and scanning strategy controls both the saturation magnetization and the magnetocrystalline anisotropy (direction, type and strength) of irradiated areas. The unique possibilities of this material system allow to overcome the shape anisotropy of long magnonic waveguides and stabilize

Spin-wave spectroscopy of individual ferromagnetic nanodisks

“…[1][2][3] This expansion is triggered by the development of advanced synthesis methods 4,5 and the discovery of novel geometry-and topologyinduced effects. 6 Among the various nanofabrication techniques, focused electron beam-induced deposition (FEBID) has unique advantages for 3D nanomagnetism, 2,3,7 magnonics 8,9 and superconducting electronics of the fluxonic type 10,11 as the magnetic properties of direct-write structures can be varied by selecting a writing strategy and beam parameters, 5 as well as via post-growth irradiation of structures with ions [12][13][14] and electrons. 15 In the context of superconductivity, hybrid ferromagnet/superconductor structures are used for the manipulation of magnetic flux quanta 16,17 and provide access to investigations of odd-frequency spin-triplet superconductivity.…”

Spin-wave eigenmodes in direct-write 3D nanovolcanoes

“…[2][3][4]9,[28][29][30][31][32][33] For magnonics, the propagation of spin waves in direct-write Fe-and Co-based conduits has recently been demonstrated, with a spin-wave decay length in the range of 3-6 lm. 34,35 Given FEBID's lateral resolution down to 10 nm and its versatility regarding the substrate material, FEBID appears as a promising nanofabrication technology for 3D magnonics. 36 Here, we investigate the spin-wave eigenmodes in individual direct-write Co-Fe nanovolcanoes by spin-wave resonance (SWR) spectroscopy 37,38 and analyze the experimental data with the aid of micromagnetic simulations.…”

Advances in Magnetics Roadmap on Spin-Wave Computing

“…This anisotropy is strong enough to stabilize the magnetization in the direction perpendicular to the long axis of narrow waveguides. It has been recently demonstrated that in this system, spin waves can propagate in favorable Damon-Eshbach mode with high group velocities reaching almost 6 km/s in orthogonally magnetised waveguides without the necessity of applying the external magnetic fields [199]. The magnetic anisotropy can also be used to stabilize various spin structures unachievable in common material systems, and these spin structures can be further used to control spin-wave propagation [200].…”