Suchergebnisse

CoFeB-based ultrathin films with perpendicular magnetic anisotropy are promising for different emerging technological applications such as nonvolatile memories with low power consumption and high-speed performance. In this work, the dynamical properties of [CoFeB (tCoFeB)/Pd (10 Å)]5 multilayered ultrathin films (1 Å ≤ tCoFeB ≤ 5 Å) are studied by using two complementary methods: time-resolved magneto-optical Kerr effect and broadband ferromagnetic resonance. The perpendicular magnetization is confirmed for multilayers with tCoFeB ≤ 4 Å. The effective perpendicular magnetic anisotropy reaches a clear maximum at tCoFeB = 3 Å. Further increase of CoFeB layer thickness reduces the perpendicular magnetic anisotropy and the magnetization became in-plane oriented for tCoFeB ≥ 5 Å. This behaviour is explained by considering competing contributions from surface and magnetoelastic anisotropies. It was also found that the effective damping parameter αeff decreases with CoFeB layer thickness and for tCoFeB = 4 Å reaches a value of ~ 0.019 that is suitable for microwave applications. ; This work was supported by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) and COMPETE 2020 (FEDER) under the projects MIT-EXPL/IRA/0012/2017, POCI-01-0145-FEDER-031302, PTDC/FIS- OTI/32213/2017, EXPL/IF/00541/2015 and UIDB/04968/2020. The authors also acknowledge financial support from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 734801 (MAGNAMED Project). The Portuguese team acknowledges the Network of Extreme Conditions Laboratories-NECL support through the project NORTE-01-0145-FEDER-022096. D.N. acknowledges the Spanish Ministry for Science, Innovation and Universities, for funding through the "Ramón y Cajal" program RYC-2017-22820. C.G. acknowledges the financial support received by ANID FONDECYT/REGULAR 1201102, ANID FONDEQUIP EQM140161, and ANID PIA/APOYO AFB180002.