A laminate of ferromagnetic films with high effective permeability at high frequencies

The paper reports on development of magnetodielectric material with high microwave permeability. The material is a laminate of multi-layer permalloy films deposited onto a thin mylar substrate by magnetron sputtering. The deposited films are arranged into a stack and glued together under pressure to obtain the laminate. With the content of ferromagnetic component in the laminate being 22 % vol., its measured quasistatic permeability is 60. The peak value of imaginary permeability attains 50 and the peak is located near 1 GHz. As compared with the multi-layer films, which the laminate is made of, it exhibits lower magnetic loss tangent at frequencies below the magnetic loss peak and may therefore be useful for many technical applications. Lower low-frequency loss may be attributed to pressing of the glued sample. This rectifies wrinkling appearing due to sputtering of rigid multi-layer film onto flexible mylar substrate and, therefore, makes the magnetic structure of the film more uniform.