Measurement of the ferromagnetic resonance of a single micron dot by using a vector network analyzer

The ferromagnetic resonance of a single micron-scale dot of permalloy was measured by using a vector network analyzer. The resonant frequency shifted to higher frequency with increasing aspect ratio of the sample. This tendency was remarkable for narrower width samples, especially the 1-µm-width dots. This means that the demagnetization effect of thin films for the ferromagnetic resonance becomes large when the sample width is less than 1 µm. The resonant frequency can be largely controlled by changing the sample width for a thin film with a width of less than 1 µm, which is a favorable characteristics for various microwave applications.