D. L. Mills

Roughness induced in plane uniaxial anisotropy in ultrathin Fe films

Abstract We have studied roughness induced in plane anisotropy, for ultrathin Fe films grown on MgO(1xa00xa00). When the films are grown, the deposition beam is directed toward the substrate at non-normal incidence, to produce a rough outer surface, with anisotropic roughness. We measure the roughness induced in plane anisotropy fields for several samples with SMOKE, and we also perform STM measurements of the actual surface profile. This allows us to calculate the roughness induced in plane anisotropy produced by the dipolar mechanism, with no adjustable parameters, using the theory of Arias and Mills. Comparison between theory and experiment shows that anisotropy of dipolar origin is a major source of extrinsic in plane anisotropy.

Theory of spin excitations and the microwave response of cylindrical ferromagnetic nanowires

We develop the theory of exchange/dipole spin wave excitations of ferromagnetic nanowires of cylindrical cross section, where the magnetization is parallel to the axis of the wire. In addition, we provide the theory of the microwave response of such structures, for the case where the nanowire is also a conductor. We present explicit calculations of both the mode structure of nanowires, and also their ferromagnetic resonance spectrum, with attention to recent experimental studies. We compare differences between the physical picture appropriate for the cylinder, with the well studied case of the ferromagnetic film.

Theory of Brillouin light scattering from ferromagnetic nanospheres

We develop the theory of Brillouin light scattering (BLS) from spin wave modes in ferromagnetic nanospheres, within a framework that incorporates the spatial variation of the optical fields within the sphere. Our recent theory of exchange dipole spin wave modes of the sphere provides us with eigenvectors. When properly normalized, these eigenvectors allow calculation of the absolute cross section of various modes which contribute to BLS spectrum. We then present explicit calculation of the BLS spectrum associated with the first few dipole/exchange spin wave modes with emphasis on their relative intensity.