Effects of Shape Anisotropy in CoO/Co/Cu/NiFe/Cu/Co Wires

Abstract

Magnetic wires consisting of the CoO/Co/Cu/NiFe/Cu/Co structures with a variable width in the range from 0.3 µm to 10 µm were fabricated by using electron-beam lithography and Ar ion milling. The width dependencies of the coercive forces in each magnetic layer and the width dependence of the exchange bias in the CoO/Co layer were investigated by using the giant magnetoresistance effect. In the Co and NiFe layers, the coercivities varied almost in proportion to the inverse wire width, and can be explained by considering the width dependencies of the demagnetic fields. In the CoO/Co layer, the coercivity enhancement of the Co layer, which may be caused by the random exchange interaction, was observed. The width dependencies of the coercive force and exchange bias in the CoO/Co layer were explained by the suppression of the fluctuation of the exchange bias. This suggests that the easy axes in the CoO layer are regulated by the shape anisotropy in the Co layer.