A mesoscopic nonmagnetic magnetoresistive read-head sensor based on the recently reported
extraordinary magnetoresistance ~EMR! effect has been fabricated from a narrow-gap Si-doped
InSb quantum well. The sensor has a conservatively estimated areal-density of 116 Gb/in.2 with a
300 K EMR of 6% and a current sensitivity of 147 V/T at a relevant field of 0.05 T and a bias of
0.27 T. Because this sensor is not subject to magnetic noise, which limits conventional sensors to
areal densities of order 100 Gb/in.2, it opens a pathway to ultra-high-density recording at areal
densities of order 1 Tb/in.2.