Confined spin waves in magnetochiral nanotubes with axial and circumferential magnetization

Abstract

We report experimental studies of spin-wave excitations in individual 22 nm thick Ni80Fe20 nanotubes with diameters of about 150 nm. We apply Brillouin light-scattering (BLS) spectroscopy under microwave irradiation and resolve sets of discrete resonances in the center of nanotubes ranging from 2.5 to 12.5 GHz. Comparing to a recent theoretical work and micromagnetic simulations, we identify different characteristic eigenmodes depending on the axial, mixed or vortex configuration. The mixed and vortex states give rise to modes with helical phase profiles substantiating an unusual nature of confined modes attributed to non-reciprocal spin waves. Our findings provide microscopic insight into realistic tubular spin-wave nanocavities and magnetochiral effects for 3D nanomagnonics.

Realization and Control of Bulk and Surface Modes in 3D Nanomagnonic Networks by Additive Manufacturing of Ferromagnets

“…[51] In Ref. [39], it has been shown that individual nanotubes with unintentional defects exhibit a multitude of resonant modes due to two discretization effects. On the one hand, spin waves undergo constructive interference along the azimuthal direction.…”

“…Further BLS experiments were performed on a bare polymer woodpile structure, which showed the same mode independent of magnetic field. Hence, this mode does not have a magnetic origin.In the following, we discuss the three field-dependent modes and compare them to magnon modes recently reported for straight and long nanotubes [39]. For this, we classified the extracted resonance frequencies into different branches (red, green, and purple symbols in Figure2a).…”

“…[38] The plasma-enhanced ALD process enabled an experimental study on the magnetochiral properties of magnons in individual permalloy nanotubes. [39] The reported properties are promising in view of 3D superstructures which exhibit engineered magnon minibands and forbidden frequency gaps in all three spatial directions. [40][41][42][43] Here, nanotubular constituent magnets provide an especially promising platform for 3D magnonics.…”

“…On the other hand, nanotubes support nonreciprocal spin waves and magnetochiral characteristics. [39,45] All these aspects promise interesting physical properties in magnonic crystals. The realization of such 3D magnonic crystals on polymeric scaffolds has not yet been achieved however.…”

Static and Dynamic Magnetic Properties of Fe3O4 Nanotubes

“…The field of magnetic nanotube synthesis has yielded a wide variety of materials that have been successfully utilized in the creation of these structures. Among the most commonly synthesized magnetic nanotubes are those made from materials such as iron (Fe) [ 8 , 9 ], Fe(OH) 3 [ 10 ], maghemite (γ-Fe 2 O 3 ) [ 10 , 11 , 12 ], magnetite (Fe 3 O 4 ) [ 10 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ], ZnFe 2 O 4 [ 19 ], CuFe 2 O 4 [ 20 ], nickel (Ni) [ 8 , 21 , 22 , 23 ], NiFe 2 O 4 [ 24 ], Ni 64 Fe 36 [ 8 ], Ni 80 Fe 20 (permalloy) [ 25 ], Co [ 8 , 23 , 26 ], Co 3 O 4 [ 27 ], Co 90 Pt 10 [ 8 ], Co 75 Cr 13 Pt 12 [ 8 ], and many others. In addition to these common materials, nanotubes with more complex geometries have also been synthesized, taking into consideration factors such as diameter modulations [ 28 ], multisegmented structures [ 29 ], and core–shell [ 30 , 31 , 32 , 33 ] systems.…”