Fabrication and in situ magnetoresistance measurement of a Ni point-contact in planar configuration

A test-element (TE) with a Ni point-contact (PC) in planar configuration was fabricated using an etching process with a horizontal incidence ion beam. Successive in situ measurement of the magnetoresistance (MR) was carried out in the etching apparatus without breaking the vacuum to prevent the oxidation of the PC. Observation by cross-sectional transmission electron microscopy (XTEM) showed that the etching damage at the sidewalls of the PC that may have been caused by the milling process was estimated to be 1-2 nm. The TE resistance increased as the milling time increased. An MR ratio of about 0.2% was measured. The resistance of the TE kept in the vacuum was stable for several days, but the resistance of the TE exposed to air became immediately unstable.