Microwave Magnetic Properties of NiFe Nanostrips

The dynamic excitations in the nano-sized Permalloy arrays exhibit a strong resonance mode in ferromagnetic resonance experiments (conventional as well as network analyzer based) for the magnetic field applied in the plane of the array and along the short axis and long axis of the arrays. In network-analyzer experiments, when the dc field was applied along the short axis of the arrays, the resonance frequency goes down with an increasing interstrip distance up to 1 mum and then saturates for higher values. This behavior clearly demonstrates the presence of dipolar interactions between the individual elements, resulting in the increased resonance frequency for the smaller spacing whereas when the field is applied along the long axis, the resonance frequencies go up with increasing interstrip distance.