Influence of Magnetic Field on Microwave Impedance of Composite Films (CoFeB+SiO2)

Radio Frequency (RF) impedance of metal- dielectric films {[(CoFeB)x+(SiO2)
(1-x)
], x=0.76, 0.88, 0.9} in the frequency range 0.1-3 GHz at room temperature were obtained in the work. Magnetic phase contrast (MPC) images of film surface fragments were obtained using an atomic force microscope. A stripe magnetic structure in the film at x=0.76 before and after magnetization of the film in a magnetic field of 0.7 Tesla was discovered. The clarity of the magnetic domain structure image after magnetization of this film was observed to decrease. Deep minima of the magnetic impedance M (f) in the frequency range 1-2.5 GHz were observed in the studied composite films. The depth of the magnetic impedance minima for all films in the M(f) dependence decreases with increasing induction of the magnetic field in which the film is located, it was shown. The minima of M(f) for films at x=0.76 shift towards lower frequencies after magnetization of the films under the influence of a magnetic field Bo=0.7 T. The M(f) minima for films at x=0.88 do not shift under the influence of a magnetic field. This film at x=0.88 is characterized by the presence of extended inhomogeneous magnetic stripes, which significantly reduce the microwave mobility of the magnetic structure. The shift in the minimum of the microwave spectrum and the decrease in the amplitude of the minimums are associated with a change in the magnetic structure of the films when they are magnetized in a magnetic field of 0.7 Tesla.