Shape-induced bi-stable magnetic states in submicrometer structures of permalloy films

We pattern submicrometer structures of thin films of permalloy in the form of two crossing ellipses and in the form of one long ellipse crossed by several ellipses where the width of the ellipses varies between 100 and 1000 nm. We find that the crossing area has two stable axes of magnetization, which are perpendicular to each other and which are rotated by 45 degrees relative to the axes of the ellipses. We measure the planar Hall effect (PHE) of the submicrometer structures and demonstrate sharp switching behavior between the two easy axes of the magnetization. The observed behavior is modeled analytically with bi-axial magnetic anisotropy and compared with numerical simulations. We discuss possible application of such submicrometer structures for PHE-based magnetic memory.