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

• Published in: Scientific reports Vol. 11; no. 1; p. 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: Journal Article
• Language: English
• Published: England Nature Publishing Group 08.01.2021; Nature Publishing Group UK; Nature Portfolio
• Subjects: Anisotropy; Power consumption
• 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 )/Pd (10 Å)] multilayered ultrathin films (1 Å ≤ t  ≤ 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  ≤ 4 Å. The effective perpendicular magnetic anisotropy reaches a clear maximum at t  = 3 Å. Further increase of CoFeB layer thickness reduces the perpendicular magnetic anisotropy and the magnetization became in-plane oriented for t  ≥ 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 decreases with CoFeB layer thickness and for t  = 4 Å reaches a value of ~ 0.019 that is suitable for microwave applications.