| 1. |
- Tacchi, S., et al.
(författare)
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Brillouin light scattering investigations of films and magnetic tunnel junctions with perpendicular magnetic anisotropy at the CoFeB-MgO interface
- 2021
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Ingår i: Journal of Physics D-Applied Physics. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 54:13
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Tidskriftsartikel (refereegranskat)abstract
- Alternating gradient force magnetometry and Brillouin light scattering (BLS) experiments were exploited to investigate the perpendicular magnetic anisotropy (PMA) localized at the CoFeB-MgO interface, both in Ta/CoFeB/MgO heterostructures (bottom samples) and in the inverted ones MgO/CoFeB/Ta (top samples). Thermal treatment was found to induce a marked increase of the PMA with respect to the as grown state. Using linear spin wave theory, an analysis of the spin wave frequencies was performed which allowed to estimate the thickness dependence of the PMA in the single CoFeB film. Magnetic tunnel junctions with the Ta/CoFeB/MgO/CoFeB/Ta structure were also studied by BLS. The analysis of the experimental results, performed via the linear spin wave theory, revealed that there is an antiferromagnetic interlayer exchange coupling between the free and the fixed CoFeB layers which increases after the annealing procedure.
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| 2. |
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| 3. |
- Tacchi, S., et al.
(författare)
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Co/Pd -CoFeB exchange spring magnets with tunable gap of spin wave excitations
- 2014
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Ingår i: Journal of Physics D-Applied Physics. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 47:49
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Tidskriftsartikel (refereegranskat)abstract
- Exchange spring magnets, consisting of a [Co(0.5 nm)/Pd(1 nm)](5) multilayer with perpendicular magnetic anisotropy and a Co20Fe60B20 film with easy plane anisotropy, of variable thickness t(CFB), are investigated using Brillouin light scattering. On reducing t(CFB) in the range 0.8-2.3 nm, the spin-wave frequency gap displays a remarkable increase from nearly 4-48 GHz, reflecting the corresponding rapid growth of the tilting angle of the magnetization with respect to the film normal. These findings are interpreted using a one-dimensional model in which each atomic layer is assumed to be uniformly magnetized, subjected to an effective out-of-plane or easy-plane anisotropy depending on the layer position in the stack, and exchange coupled to its two nearest neighbour atomic layers. With respect to previously investigated [Co/Pd]-NiFe hybrid magnets, a largest frequency tunability, restricted to a narrower range of the soft layer thickness, is observed.
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| 4. |
- Tacchi, S., et al.
(författare)
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Spin wave excitations in exchange-coupled [Co/Pd]-NiFe films with tunable tilting of the magnetization
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 87:14, s. 144426-
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Tidskriftsartikel (refereegranskat)abstract
- Brillouin light scattering was applied to measure the evolution of spin waves in exchange-coupled [Co/Pd]-NiFe films with out-of-plane/in-plane magnetic anisotropy. Tunable tilting of the magnetization has important effects on the spin wave frequency gap: a substantial increase is observed with decreasing the soft NiFe thickness, while seemingly insignificant tilting angles cause a strong reduction with respect to a film with only the hard [Co/Pd] component. The spin wave frequency is reproduced also in samples, with increased thickness of the upper Pd layer, where a sudden modification in the tilting at the hard/soft interface is caused by the weakening of interlayer exchange.
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