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- Brucas, R., et al.
(författare)
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Magnetic anisotropy and evolution of ground-state domain structures in bcc Fe81Ni19/Co(001) superlattices
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : The American Physical Society. - 1098-0121 .- 1550-235X. ; 78:2, s. 024421-
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic anisotropy and evolution of striped magnetic domain structures in bcc Fe81Ni19/Co(001) superlattices with the total thickness ranging from 85 to 1370 nm has been studied by magneto-optical Kerr effect and magnetic force microscopy. At a thickness of about 85 nm [25 bilayers (BL)] the domains appear as stripe domains, typical for perpendicular anisotropy films, with the weak cubic anisotropy of the in-plane magnetization component stabilizing the stripe direction. The magnetic domain period strongly depends on the thickness of the superlattice. As the thickness increases, the equilibrium magnetization orients at oblique angles with respect to the film plane and continuously varies with the thickness from in-plane to out-of-plane. We first apply a simple phenomenological model which correctly predicts the transition from in-plane to out-of-plane magnetization as well as increasing domain period and saturation field with increasing BL number. The results indicate the presence of partial flux-closure domains at the film surface with the tilt angle continuously varying with the superlattice thickness. By solving a linearized Landau–Lifshitz equation together with Maxwell’s equations in magnetostatic approximation for samples consisting of up to 1000 individual layers, we calculate the spin-wave dispersion and determine the stability conditions for the saturated ferromagnetic state. From these results the dependence of the saturation field on the number of layers is inferred and agrees well with the experiment. The uniaxial bulk anisotropy is attributed to distortions along the c axis and the results further show evidence for the presence of an easy-plane interface anisotropy in these samples.
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- Brucas, R., et al.
(författare)
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Magnetization and domain structure of bcc Fe81Ni19/Co (001) superlattices
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 69:6, s. 064411/1-064411/11
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Tidskriftsartikel (refereegranskat)abstract
- Dense stripe domains were obsd. for a Fe81Ni19/Co superlattice grown on a MgO(100) single crystal substrate using dc magnetron sputtering. The stripe domain period exhibits irreversible changes with the magnetic field, as detd. by magnetic force microscopy. We present a simple theor. model for this system and calc. the magnetization and domain period as functions of the applied field by minimizing the total energy. For this purpose, an expression for the domain wall energy and wall width for arbitrary angles and one for the magnetostatic energy are derived. The model correctly predicts a decreasing domain period with the increasing applied field. At larger magnetic fields a transition to "chaotic" two-dimensional stripe patterns is obsd. and a qual. discussion of this phenomenon is given.
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- Haferman, H., et al.
(författare)
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Competing anisotropies in bcc Fe81Ni19/Co(001) superlattices
- 2009
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:7, s. 073102-073102-3
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Tidskriftsartikel (refereegranskat)abstract
- Amagnetization reorientation transition has been observed in Fe81Ni19/Co(001) superlattices bymeans of magneto-optical Kerr effect and magnetic force microscopy measurements.The transition is driven by the variation of the interfacedensity. First-principles calculations are combined with a linear stability analysisof the Landau–Lifshitz equation to clarify the mechanism that drivesthe transition. We are able to identify it as beingdriven by competing interface in-plane and uniaxial bulk out-of-plane anisotropies.The origin of the bulk anisotropy is attributed to tetragonaldistortions experimentally observed in these superlattices.
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