Reorientational magnetic transition in mesoscopic cobalt dots

We have measured magnetic anisotropy constants and domain structures in arrays of magnetic dots 0.5 mu m wide fabricated out of an epitaxial (0001) hcp cobalt film. Occurrence of a concentric stripe domain pattern for which the magnetization is mostly in-plane with small alternately up and down perpendicular components is found for a 25-nm-thick cobalt dot array. Interestingly, this sample produces a spin reorientation from a quasi in-plane to a fully perpendicularly oriented magnetization when the temperature is lowered, due to an increase of the perpendicular anisotropy at low temperature. (C) 1997 American Institute of Physics. [S0003-6951(97)00145-9].