A magnetoresistive sensor having a magnetically anisotropic pinned layer structure. The pinned layer structure is formed over a seed layer having a surface that has been treated to texture the surface of the seed layer with an anisotropic roughness. This anisotropic roughness induces the magnetic anisotropy in the pinned layers. The treated seed layers also allow the pinned layer to maintain robust pinning without the need for a thick AFM layer, thereby reducing gap size.