J Supercond Nov Magn (2017) 30:469–473 DOI 10.1007/s10948-016-3730-9 ORIGINAL PAPER Ferromagnetic Relaxation and Magnetic Properties of Co 40 Fe 40 B 20 Thin Films Naeem Ahmad 1,2 · Tian YU 3 · Suleman Khan 1 · Abdul Majid 4 · Javed Iqbal 5 · Saqlain A. Shah 6 · S. U. Awan 7 · X. F. Han 2 Received: 20 July 2016 / Accepted: 13 August 2016 / Published online: 7 September 2016 © Springer Science+Business Media New York 2016 Abstract The Co 40 Fe 40 B 20 thin films with varying thick- ness using silicon dioxide (SiO 2 ) as substrate were fabri- cated by magnetron sputtering system (ULVAC, Japan) with a base pressure P = 10 −8 Torr to understand magnetody- namic interactions and structural properties. The samples were characterized using X-band ferromagnetic resonance experiments at room temperature. The XRD pattern shows that the thin film is amorphous and we got a strong peak (400) of substrate silicon dioxide (SiO 2 ). The SEM result of Co 40 Fe 40 B 20 thin film demonstrates that it has uniform and homogeneous morphology. It has been observed from ferromagnetic resonance (FMR) results that the thin film depicts anisotropic behavior and easy axis lies out of the plane. The dependence of the resonance fields on the angle  Naeem Ahmad naeem.ahmad@iiu.edu.pk 1 Spintronics Laboratory, Department of Physics, International Islamic University, Islamabad, 44000, Pakistan 2 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences (CAS), Beijing 100190, China 3 College of Physical Science and Technology, Sichuan University, Chengdu, 610064, China 4 Department of Physics, University of Gujrat, Gujrat, Pakistan 5 Department of Physics, Quaid-i-Azam University, Islamabad, Pakistan 6 Department of Physics, Forman Christian College (University), Lahore, Pakistan 7 Department of Physics, COMSATS Institute of Information Technology, Islamabad, 45320, Pakistan between the normal of the film and out of plane dc magnetic field indicates the presence of uniaxial magnetic anisotropy associated with thickness of Co 40 Fe 40 B 20 thin films. The inplane and out-of-plane angular dependences of the res- onance field (H R ) and line width (H pp ) of FMR spectra were measured and explained using the Landau–Lifshitz– Gilbert equation. The origin of magnetic damping has been discussed by considering spin–orbit, s–d interactions, and two magnonscattering mechanism. Some background molecular vibrations at wave number 2000 and 3800 cm −1 in three samples are also identified from FTIR, which fur- ther show that background molecular vibrations can be reduced by decreasing the size. This study will be helpful to understand spin transfer torque (STT) and the timescale for magnetization reversal in the spintronic devices Keywords Ferromagnetic thin films · Ferromagnetic relaxation · LLG equatation 1 Introduction In the recent years, soft magnetic CoFeB thin films have attracted a lot of attention due to large tunneling magne- toresistance ratio (TMR) and spin transfer torque (STT) in magnetic random access memory (MRAM) using magnetic tunnel junctions (MTJs). The CoFeB thin films usually do not have a pinning center and are amorphous due to the pres- ence of boron atoms. Beside it, the smooth CoFeB interfaces are perfect for the growth of ultrathin barrier layers due to its amorphous nature, thus, making CoFeB an ideal ferro- magnetic electrode with low-resistance area (RA) product for MTJs. In addition, the CoFeB/MgO combinations are promis- ing candidates for current-induced magnetization switching