Finite size effects in patterned magnetic permalloy films

Electron beam lithography has been used to prepare 250-A-thick square-shape d permalloy dots whose width and separation are in the range between 1 and 4 mu m. The static and dynamic magnetic properties of these structures have been investigated by complementary techniques such as magneto-optic Kerr e ffect (MOKE), magnetic force microscopy (MFM), and Brillouin light scatteri ng (BLS). Longitudinal MOKE enabled us to compare the hysteresis loops of t he specimens with different dot size and interdot separation, showing a mar ked influence of the demagnetizing field inside the dots. MFM images record ed at zero applied field showed that, depending on the interdot spacing, th ere is a prevalence of either four- or seven-domain patterns together with a minority of nonsolenoidal patterns that possess a net magnetic moment. BL S from thermally activated spin waves were then used to determine the intri nsic magnetic parameters of the permalloy films and to show evidence of the discretization of the spin-wave peak due to the wave vector resonance cond ition within each dot. (C) 2000 American Institute of Physics. [S0021-8979( 00)38108-7].