No abstract

No abstract

Realistic calculations of linear spin waves in thin ferromagnetic stripes are presented using a microscopic method based on a Hamiltonian approach. The theory, which is applicable to inhomogeneously magnetized samples, incorporates both the exchange and dipole-dipole interactions as well as effects of single-ion anisotropy and an external magnetic field applied either parallel or perpendicular to the stripe axis. This approach does not require the specification of phenomenological boundary conditions to study spin waves in these confined configurations. The Green's function theory is applied to Permalloy and nickel stripes to obtain the frequency, spatial distribution, and spectral intensity of discrete spin-wave modes. Through the spin-wave properties, the effective pinning parameters of the dynamic magnetization at the boundaries of the systems are deduced.

Brillouin light scattering has been employed to study the magnetic-field dependence of the discrete spin waves in permalloy Ni 80 Fe 20 nanowires. When a small magnetic field is applied transverse to the nanowire, the results reveal a low-frequency mode, which is absent in the longitudinal case. A Hamiltonian-based microscopic theory for nanowires with inhomogeneous magnetization shows that the appearance of this mode, along with its higher-field behavior, is a significant consequence of a small easy-plane single-ion anisotropy at the nanowire surface. The calculations provide a good description of experimental data for both the transverse and longitudinal cases.

No abstract