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| 2. |
- Lumetzberger, Julia, et al.
(författare)
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Control of site occupancy by variation of the Zn and Al content in NiZnAl ferrite epitaxial films with low magnetic damping
- 2022
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 105:13
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Tidskriftsartikel (refereegranskat)abstract
- The structural and magnetic properties of Zn/Al doped nickel ferrite thin films can be adjusted by changing the Zn and Al content. The films are epitaxially grown by reactive magnetron sputtering using a triple cluster system to sputter simultaneously from three different targets. Upon the variation of the Zn content, the films remain fully strained with similar structural properties, while the magnetic properties are strongly affected. The saturation magnetization and coercivity as well as resonance position and linewidth from ferromagnetic resonance (FMR) measurements are altered depending on the Zn content in the material. The reason for these changes can be elucidated by investigation of the x-ray magnetic circular dichroism spectra to gain site- and valence-specific information with elemental specificity. Additionally, from a detailed investigation by broadband FMR, a minimum in g factor and linewidth could be found as a function of film thickness. Furthermore, the results from a variation of the Al content using the same set of measurement techniques is given. Other than for Zn, the variation of Al affects the strain and even more pronounced changes to the magnetic properties are apparent.
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| 3. |
- Lumetzberger, Julia, et al.
(författare)
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Influence of structure and cation distribution on magnetic anisotropy and damping in Zn/Al doped nickel ferrites
- 2020
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 102:5
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Tidskriftsartikel (refereegranskat)abstract
- An in-depth analysis of Zn/Al-doped nickel ferrites grown by reactive magnetron sputtering is relevant due to their promising characteristics for applications in spintronics. The material is insulating and ferromagnetic at room temperature with an additional low magnetic damping. By studying the complex interplay between strain and cation distribution their impact on the magnetic properties, i.e., anisotropy, damping, and g-factor is unravelled. In particular, a strong influence of the lattice site occupation of Ni-Td(2+) and cation coordination of Fe-Oh(2+), on the intrinsic damping is found. Furthermore, the critical role of the incorporation of Zn2+ and Al3+ is evidenced by comparison to a sample of altered composition. Specifically, the dopant Zn2+ is evidenced as a tuning factor for Ni-Td(2+) and therefore unquenched orbital moment directly controlling the g-factor. A strain-independent reduction of the magnetic anisotropy and damping by adapting the cation distribution is demonstrated.
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| 4. |
- Neeraj, Kumar, et al.
(författare)
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Inertial spin dynamics in ferromagnets
- 2021
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2473 .- 1745-2481. ; 17, s. 245-250
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Tidskriftsartikel (refereegranskat)abstract
- The understanding of how spins move and can be manipulated at pico- and femtosecond timescales has implications for ultrafast and energy-efficient data-processing and storage applications. However, the possibility of realizing commercial technologies based on ultrafast spin dynamics has been hampered by our limited knowledge of the physics behind processes on this timescale. Recently, it has been suggested that inertial effects should be considered in the full description of the spin dynamics at these ultrafast timescales, but a clear observation of such effects in ferromagnets is still lacking. Here, we report direct experimental evidence of intrinsic inertial spin dynamics in ferromagnetic thin films in the form of a nutation of the magnetization at a frequency of ~0.5 THz. This allows us to reveal that the angular momentum relaxation time in ferromagnets is on the order of 10 ps.
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| 5. |
- Salikhov, Ruslan, et al.
(författare)
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Coupling of terahertz light with nanometre-wavelength magnon modes via spin-orbit torque
- 2023
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2473 .- 1745-2481. ; 19:4, s. 529-535
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Tidskriftsartikel (refereegranskat)abstract
- Spin-based technologies can operate at terahertz frequencies but require manipulation techniques that work at ultrafast timescales to become practical. For instance, devices based on spin waves, also known as magnons, require efficient generation of high-energy exchange spin waves at nanometre wavelengths. To achieve this, a substantial coupling is needed between the magnon modes and an electro-magnetic stimulus such as a coherent terahertz field pulse. However, it has been difficult to excite non-uniform spin waves efficiently using terahertz light because of the large momentum mismatch between the submillimetre-wave radiation and the nanometre-sized spin waves. Here we improve the light–matter interaction by engineering thin films to exploit relativistic spin–orbit torques that are confined to the interfaces of heavy metal/ferromagnet heterostructures. We are able to excite spin-wave modes with frequencies of up to 0.6 THz and wavelengths as short as 6 nm using broadband terahertz radiation. Numerical simulations demonstrate that the coupling of terahertz light to exchange-dominated magnons originates solely from interfacial spin–orbit torques. Our results are of general applicability to other magnetic multilayered structures, and offer the prospect of nanoscale control of high-frequency signals.
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