Magnetoresistance and planar Hall effects in submicron exchange-coupled $NiO/Fe19Ni81$ wires

Magnetization reversal processes of submicron $NiO/Fe19Ni81$ exchange-coupled Hall cross with a variable width in the range from 0.2 to 0.4 μm were studied by the magnetoresistivity and the planar Hall effect measurements. The magnetization reversal was found to take place via a coherent rotation in the Hall cross, suggesting that the size of the antiferromagnetic domain is regulated by the wire width. The magnitude of the exchange coupling field $Hex$ varied in proportion to the inverse wire width.