MR HEAD RESPONSE FROM ARRAYS OF LITHOGRAPHICALLY PATTERNED PERPENDICULAR NICKEL COLUMNS

We report, for the first time, the MR head response from lithographica lly patterned perpendicular nickel columns. Electron-beam lithography is used to fabricate arrays of Ni columns, 400 nm tall and 150 nm in d iameter spaced 2.1 mu m apart, embedded in SiO2, The sample surface is planarized with a chemical mechanical polish, The technique of Scanni ng Magnetoresistance Microscopy (SMRM), in which a magnetoresistive (M R) head is raster-scanned in contact with a sample, is used to investi gate the MR head response from the Ni columns, Single columns can be ' 'read'' with a 0-peak MR voltage of 60-70 mu V. Unexpectedly, we find that the magnetic field due to the bias current in the MR head is enou gh to switch the columns during scanning, which results in a ''digit-l ike'' MR response, By scanning in the presence of a small (similar to 21Oe) external magnetic bias field, the columns can be imaged in eithe r their ''up'' or ''down'' magnetic states.