Periodic Reporting for period 1 - SUPER-MAGNONICS (Coupling of magnetization dynamics and superconducting state in artificial superconductor/ferromagnet hybrid structures)
Reporting period: 2020-09-01 to 2022-08-31
The project addresses a problem that has received very little experimental attention despite its fundamental and technological interest: the coupling between superconducting state and magnetization dynamics in artificial superconductor (S) / ferromagnet (F) hybrid structures. The interplay between superconductors and ferromagnets leads to a rich variety of phenomena, which span from the nanoscale confinement of the superconducting condensate to the emergence of unconventional (equal-spin triplet) superconductivity. Two main classes of mechanisms are behind that rich phenomenology: electromagnetic effects (e.g. field screening effects, which dictate the interaction between flux quanta in S and the stray field from F) and “electronic” ones (e.g. penetration of superconducting pairs6 from S into F).
The project has important technological implications in non-dissipative spintronics devices, which exploit the spin degree of freedom to store information with the non-dissipative character of the superconducting condensate.
The objectives are:
WP1: Design an experiment based on S/F hybrids to study the excitation and detection of magnons via dc electrical transport.
WP2: Spin pumping via ferromagnetic resonance (FMR) and Inverse Spin Hall effect (ISHE) at S/F interfaces. In this part the goal is to experimentally determine the role of i) the generation of spin-triplet correlations and ii) quasiparticle spin-pumping/diffusion on the coupling between the superconducting state and the magnetization dynamics.
The project has important technological implications in non-dissipative spintronics devices, which exploit the spin degree of freedom to store information with the non-dissipative character of the superconducting condensate.
The objectives are:
WP1: Design an experiment based on S/F hybrids to study the excitation and detection of magnons via dc electrical transport.
WP2: Spin pumping via ferromagnetic resonance (FMR) and Inverse Spin Hall effect (ISHE) at S/F interfaces. In this part the goal is to experimentally determine the role of i) the generation of spin-triplet correlations and ii) quasiparticle spin-pumping/diffusion on the coupling between the superconducting state and the magnetization dynamics.
WP1. Microwave excitation and dc transport detection in S/F hybrids.
Work performed: In this part we design and tested an experiment to excite spin waves in a ferromagnetic coplanar waveguide (CPW) and study the stray field created by the collective excitations with the periodic field modulation created by a vortex lattice in an adjacent type II superconductor.
Main results: The main scientific and technological achievement of this WP is the possibility to detect spin waves at cryogenics temperatures, despite the linewidth broadening of the YIG. The experience acquired in the fabrication and characterization of these devices provides a good base ground to conceive magnonic filters based on s-wave or even high Tc superconductors.
Exploitation of the results: The host institution will exploit these results in the short term, in a new research line dedicated to superconductor/ferromagnet hybrids, and in the middle period to the dedicated scientific community. In the long term, these results are expected to be exploited in the RF industry of communications.
WP2. Spin pumping via ferromagnetic resonance (FMR) and Inverse Spin Hall effect (ISHE) at S/F interfaces.
Work performed: Here we conducted ferromagnetic resonance and Inverse Spin Hall effect experiments to characterize the electronic coupling between the superconducting state and the magnetization dynamics in superconductor/ferromagnet hybrids. In particular, we analyzed superconductor/ferromagnet heterostructures from three different aspects,
i) the generation of spin-triplet correlations
ii) quasiparticle spin-pumping/diffusion and
iii) The performance of d-wave superconductors for non-dissipative spin transport and the influence of the gap anisotropy.
Main results:
1. We showed the influence of the d-wave gap anisotropy on the spin pumping efficiency in d-wave superconductor/ferromagnet heterostructures.
2. We found a large spin-to-charge conversion efficiency in YIG/s-wave SC using local detection methods.
3. We developed a novel growth process to integrate garnets and perovskites in hybrids systems.
4. We provided evidence that suggests the presence of spin-triplet supercurrents detected from spin-pumping experiments in d-wave superconductor/ferromagnet hybrids.
Exploitation of the results for both WPs: The host institution will exploit these results in the short term, in a new research line dedicated to superconductor/ferromagnet hybrids, and in the middle period to the dedicated scientific community. In the long term, these results are expected to be exploited in the RF industry of communications.
Work performed: In this part we design and tested an experiment to excite spin waves in a ferromagnetic coplanar waveguide (CPW) and study the stray field created by the collective excitations with the periodic field modulation created by a vortex lattice in an adjacent type II superconductor.
Main results: The main scientific and technological achievement of this WP is the possibility to detect spin waves at cryogenics temperatures, despite the linewidth broadening of the YIG. The experience acquired in the fabrication and characterization of these devices provides a good base ground to conceive magnonic filters based on s-wave or even high Tc superconductors.
Exploitation of the results: The host institution will exploit these results in the short term, in a new research line dedicated to superconductor/ferromagnet hybrids, and in the middle period to the dedicated scientific community. In the long term, these results are expected to be exploited in the RF industry of communications.
WP2. Spin pumping via ferromagnetic resonance (FMR) and Inverse Spin Hall effect (ISHE) at S/F interfaces.
Work performed: Here we conducted ferromagnetic resonance and Inverse Spin Hall effect experiments to characterize the electronic coupling between the superconducting state and the magnetization dynamics in superconductor/ferromagnet hybrids. In particular, we analyzed superconductor/ferromagnet heterostructures from three different aspects,
i) the generation of spin-triplet correlations
ii) quasiparticle spin-pumping/diffusion and
iii) The performance of d-wave superconductors for non-dissipative spin transport and the influence of the gap anisotropy.
Main results:
1. We showed the influence of the d-wave gap anisotropy on the spin pumping efficiency in d-wave superconductor/ferromagnet heterostructures.
2. We found a large spin-to-charge conversion efficiency in YIG/s-wave SC using local detection methods.
3. We developed a novel growth process to integrate garnets and perovskites in hybrids systems.
4. We provided evidence that suggests the presence of spin-triplet supercurrents detected from spin-pumping experiments in d-wave superconductor/ferromagnet hybrids.
Exploitation of the results for both WPs: The host institution will exploit these results in the short term, in a new research line dedicated to superconductor/ferromagnet hybrids, and in the middle period to the dedicated scientific community. In the long term, these results are expected to be exploited in the RF industry of communications.
Long-range spin transport in superconductors is highly desirable for energy harvesting in spintronics due to its virtually non-dissipation character. In this scenario, the work done so far showed that we can exploit the interaction between collective magnetic excitations (spin waves) in ferrimagnetic insulators like YIG with the stray fields and the density of states of an adjacent superconductor to build non-dissipative devices operable in the radiofrequency range. In particular, we proved that non-equilibrium spin accumulation can be detected over long-range distances using a local detection method based on the spin-to-charge conversion, frequency-dependent FMR measurements with coplanar waveguides give an effective and easy way to test the spin absorption efficiency of a superconductor and the use of d-wave superconductors looks promising as a conduit for spin propagation due to its anisotropic spin absorption efficiency, its high critical temperature and the possibility to propagate spin-triplet Cooper pairs over long distances.