High frequency high field permeability of patterned Ni₈₀Fe₂₀ and Ni₄₅Fe₅₅ thin films

High frequency high field permeability of patterned Ni80Fe20 and Ni45Fe55 thin films was measured from lithographically defined toroids. Measurement frequency is up to 500 MHz and excitation field up to 5 Oe. Permeability rolloff is calculated from the inductance data. In this experiment, patterned widths range from 30 down to 0.5 μm. Our data suggest that the rotational permeability measured at low field excitation is sufficient to predict high frequency characteristics. The rotational permeability decreases with decreasing patterned width. The 0.5 μm wide permalloy device has μ of 80 and the Ni45Fe55 50. © 2001 American Institute of Physics.