Dynamical behaviour of ultrathin [CoFeB (tCoFeB)/Pd] films with perpendicular magnetic anisotropy

• Published in: Scientific reports 2021-01, Vol.11 (1), p.43-43, Article 43
• Main Authors: Silva, Ana S., Sá, Simão P., Bunyaev, Sergey A., Garcia, Carlos, Sola, Iñigo J., Kakazei, Gleb N., Crespo, Helder, Navas, David
• Format: Article
• Language: English
• Subjects: 639/301; 639/766; 639/925; Anisotropy; Humanities and Social Sciences; multidisciplinary; Power consumption; Science; Science (multidisciplinary)
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-79632-0

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 ( t CoFeB )/Pd (10 Å)] 5 multilayered ultrathin films (1 Å ≤  t CoFeB  ≤ 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 t CoFeB  ≤ 4 Å. The effective perpendicular magnetic anisotropy reaches a clear maximum at t CoFeB  = 3 Å. Further increase of CoFeB layer thickness reduces the perpendicular magnetic anisotropy and the magnetization became in-plane oriented for t CoFeB  ≥ 5 Å. This behaviour is explained by considering competing contributions from surface and magnetoelastic anisotropies. It was also found that the effective damping parameter α eff decreases with CoFeB layer thickness and for t CoFeB  = 4 Å reaches a value of ~ 0.019 that is suitable for microwave applications.