a magnetic sensor having a first sensor stack portion that includes a free layer , non - magnetic spacer or barrier layer and a portion of a pinned layer structure . the sensor has second sensor stack portion formed over the first sensor stack portion . the second sensor stack portion include includes a second portion of the pinned layer structure and a layer of antiferromagnetic material formed over the . the first sensor stack portion is configured with a width and stripe height that define the functional width and strip height of the sensor , whereas the upper portion can be made wider and deeper without affecting sensor performance . because the patterning of the first sensor stack portion is performed on a thinner structure than would be necessary to pattern the entire sensor stack , the patterning can be performed with smaller dimensions and increased resolution .