Spin wave ballistic transport properties of [Co1−cGdc]ℓ′[Co]ℓ[Co1−cGdc]ℓ′[Co1−cGdc]ℓ′[Co]ℓ[Co1−cGdc]ℓ′ nanojunctions between Co leads

• Modeling spin wave scattering at cobalt–gadolinium alloy nanojunctions.
• Calculations yield localized and resonant spin modes on the nanojunctions.
• Spin wave ballistic transport spectra present resonance assisted maxima.
• Model applies to transmission spectra for submicroscopic magnonics.
• Scattering spectra change with nanojunction thickness and alloy concentration.

The spin wave (SW) ballistic transport properties are investigated for nanojunction systems composed of thin [Co1−cGdc]ℓ′[Co]ℓ[Co1−cGdc]ℓ′[Co1−cGdc]ℓ′[Co]ℓ[Co1−cGdc]ℓ′ layered nanostructures between cobalt leads. The nanojunction is considered as a homogeneous random alloy of concentrations c on an hcp crystal lattice. ℓ corresponds to the numbers of the hcp (0001) atomic planes per given layer. The phase field matching theory (PFMT) is used to investigate the spin dynamics of the nanojunction system in the virtual crystal approximation (VCA), valid in particular for submicroscopic SW wavelengths. The model calculations yield the spin modes localized on the nanojunction, normal to its plane, in their propagating and resonant forms. The eigenvectors of these modes are calculated for certain cases to illustrate the spin precession configurations on the nanojunction. The VCA-PFMT approach yields a general model, and is used to calculate the SW ballistic scattering and transport across the nanojunction for spin waves incident from the Co leads onto the nanojunction. The results demonstrate resonance Fano assisted maxima in the SW transmission spectra due to interactions between incident lead spin waves and localized spin resonances on the nanojunction. It is shown that these maxima change with nanojunction thickness and alloy concentration. The spectral transmission results for low frequency SWs are of specific interest, in particular they correspond to submicroscopic wavelengths which present an interest for current research of magnonic devices.