We report plasma-enhanced atomic layer deposition (ALD) to prepare conformal nickel thin films and nanotubes using nickelocene as a precursor, water as the oxidant agent, and an incycle plasma-enhanced reduction step with hydrogen. The optimized ALD pulse sequence, combined with a post-processing annealing treatment, allowed us to prepare 30 nm-thick metallic Ni layers with a resistivity of 8 μΩ cm at room temperature and good conformality both on the planar substrates and nanotemplates. Thus, we fabricated several micrometers-long nickel nanotubes with diameters ranging from 120 to 330 nm. We report the correlation between ALD growth and functional properties of individual Ni nanotubes characterized in terms of magnetotransport and the confinement of spin-wave modes. The findings offer novel perspectives for Ni-based spintronics and magnonic devices operated in the GHz frequency regime with 3D device architectures.

Permalloy Ni80Fe20 is one of the key magnetic materials in the field of magnonics.

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.

We report experimental studies of spin-wave excitations in individual 22 nm thick Ni80Fe20 nanotubes with diameters of about 150 nm by means of Brillouin light-scattering (BLS) spectroscopy. Irradiated by microwaves we 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 modes attributed to non-reciprocal spin waves. Our findings provide microscopic insight into tubular spin-wave nanocavities and magnetochiral effects for 3D nanomagnonics.

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