Study on the Magnetization Dynamics of Ni-Fe Dot Arrays Estimated by the CPW-FMR Measurement Method

This paper describes the magnetization dynamics of Ni-Fe dot array estimated by the ferromagnetic measurement with the coplanar waveguide. The magnetic configuration of the dot changes from a multi-domain to a closure domain as the dot size decreases. The switching field at which a single domain is formed increases with the dot size reduction, which may be attributed to the enhanced magnetostatic energy. On the other hand, the damping constant decreases monotonically from 0.029 to 0.012 for the major axis length < 1μm , and their values are higher than that of the Ni-Fe film (α =0.009 ). The reason for these differences is that the demagnetization field distribution near the dot edge becomes inhomogeneous with the dot size reduction. On the basis of these results, it is revealed that the extrinsic factor, such as the inhomogeneous demagnetization field distribution, strongly influences on the damping constant. These results also suggest that the correlation with the magnetic configuration of the dot is one of the most important to understand the magnetization dynamics in submicrometer-sized magnets in detail.