Sub-micron GMR sensors with vertically integrated hard magnet biasing applicable for high temperature operation

This paper demonstrates high-temperature operation of a sub-micron GMR sensor, biased with a vertically integrated hard magnet. In the present study, fringe fields from vertically integrated CoPt pattern are used for biasing transverse to the short axis of the GMR strip. While, well-defined shape anisotropy in the narrow strip pattern is used for biasing parallel to the short axis. A sputtered Co/Cu multilayer overlaid with CoPt is structured into strip pattern with a width of down to 0.4 μm by electron beam lithography and Ar ion milling. A typical layer structure of the studied samples is [Co(2.0 nm)/Cu(2.0 nm)]/Ta(8.0 nm)/CoPt(23 nm). The fabricated self-biased GMR strip exhibited superior linear MR response to alternative external fields ranged from 0.4 to 250 Oe at room temperature and 553 K (apparatus limit)