High-Frequency Permeability of Composite Anisotropic Multilayers

We have investigated a double-structured four-layered composite anisotropic film with the aim of obtaining advanced properties for practical use. The film composition was {[CoNbZr(250 nm)/SiO2(20 nm)]4/ SiO2(t)}4, with a shift angle of 45°. The sample was annealed in a weak rotating miagnetic field. The total thickness of the metal layers was 4.0 ¿m, with an optimum SiO2 thickness. The film permeability showed a flat frequency response and small temperature coefficient. A larger SiO2 layer thickness is recommended for applications. Annealing at between 200°C and 400°C resulted in a high permeability in the range of 1000 to 2000 and an excellent frequency response of ¿´ at 1 to 100 MHz in all directions within the film plane. These results may be explained in terms of the magnetic interactions of the CoNbZr magnetic layers, which are in close contact with one another through the intervening SiO2 layers.