Bottom IrMn-based spin valves by using oxygen surfactant

Abstract

Bottom IrMn-based spin valves through exposure of part of the CoFe pinned layer to O-2 with the structure Ta30/NiFe20/IrMn70/CoFet/oxidation/CoFe(30-t)/Cu20/CoFe30/Ta35 (all thickness in angstroms) (oxidation indicates exposure to different O-2 flows) were deposited by dc magnetron sputtering on thermally oxidized Si (111) substrates. Within the range of O-2 flows (0.4-2.8 sccm) studied, the value of the magnetoresistance (MR) ratio is seen to be quite low at a relatively large t of >16 Angstrom and a exchange coupling field (H-ex) decreases when the O-2 exposed CoFe surface is too close to IrMn. Under optimal conditions, a MR ratio of 8.6% with H(ex)similar to275 Oe for the bottom single spin valve and a MR ratio 12.2% with H(ex)similar to268/220 Oe for the dual spin valve are obtained. X-ray reflectivity data show smoother interfaces for the spin valves subjected to O-2 exposure. The enhanced MR ratio coupled with the lower interlayer coupling field (H-int), sheet resistance, and magnetic moment of the specular spin valve can be attributed to an enhanced specularity as a result of smoother interfaces after O-2 exposure. (C) 2003 American Institute of Physics.