The values of uniaxial anisotropy Hk in thin polycrystalline Permalloy films measured by static and dynamic methods differ by as much as a factor 1.5. The anisotropy obtained with a pulsed inductive microwave magnetometer in 2.5-100 nm thick Permalloy films exhibits an additional isotropic component of 120-240 A/m not observed in static measurements. The static anisotropy value was obtained with an inductive magnetic hysteresis loop tracer. The time-resolved precessional response was measured as a function of in-plane magnetic applied bias field and the angle between the easy-axis and the applied bias field. We interpret the constant offset field as a transient component of the magnetic anisotropy that affects only dynamical response at time scales below 10 ns.
Applied Physics Letters
time resolved, magnetic anisotropy, Permalloy, pulsed inductive microwave magnetometer