MR head response from arrays of lithographically patterned perpendicular nickel columns

Abstract

We report, for the first time, the MR head response from lithographically patterned perpendicular nickel columns. Electron-beam lithography is used to fabricate arrays of Ni columns, 400 nm tall and 150 nm in diameter spaced 2.1 μm apart, embedded in SiO2. The sample surface is planarized with a chemical mechanical polish. The technique of Scanning Magnetoresistance Microscopy (SMRM), in which a magnetoresistive (MR) head is raster-scanned in contact with a sample, is used to investigate the MR head response from the Ni columns. Single columns can be “read” with a 0-peak MR voltage of 60-70 μV. Unexpectedly, we find that the magnetic field due to the bias current in the MR head is enough to switch the columns during scanning, which results in a “dibit-like” MR response, By scanning in the presence of a small (~21 Oe) external magnetic bias field, the columns can be imaged in either their “up” or “down” magnetic states.