Permeability of narrow permalloy stripes

The effective permeability between 1 MHz and 100 MHz was measured for 1-3 μm thick permalloy(80Ni- 20Fe) films in 2-3 cm diameter sheets and compared with the effective permeability for the same films after etching them into 51μm wide stripes on 127μm centers. Solid permalloy films show a 15%-40% loss of effective permeability at all frequencies after having been etched into stripes. Permalloy films made with nonmagnetic metal laminations show no significant permeability change after etching. Films made with dielectric laminations show no significant permeability change at low frequencies and a 20%-100% increase in the high frequency permeability after etching.