Giant magnetoresistance and temperature characteristics of bottom spin valves having very thin Cu spacers

Abstract

Summary form only given. Magnetoresistance and temperature characteristics of bottom spin valves having very thin Cu spacers are reported. The spin valves were deposited using a DC magnetron sputter deposition system having a base pressure below 2/spl times/10/sup -9/ Torr. The spin valve films were annealed at 220/spl deg/C for 2 hours in 2 kOe of magnetic field. Variation of magnetoresistance (MR) ratio with respect to Cu spacer thickness is shown for underlayer55/spl Aring//NiFe10/spl Aring//IrMn70/spl Aring//CoFe10/spl Aring//Ru4/spl Aring// CoFe13/spl Aring//Cu/CoFe10/spl Aring//NiFe10/spl Aring//Ta50/spl Aring/ bottom spin valve structure. MR ratio was 11.7% at the Cu thickness of 18 /spl Aring/ and decreased to 9.8% at 12 /spl Aring/ due to the increase of the interlayer coupling field from 14 Oe to 248 Oe. Then, MR ratio increased and reached a maximum of 11.9% at the Cu thickness of 10.4 /spl Aring/, which corresponded to 12 Oe of antiferromagnetic coupling field. Unlike the top spin valves reported earlier by the authors, the dipping of the MR ratio near the zero coupling field was not observed. Also shown is the sheet resistance change (DRs) vs. Cu spacer thickness for the same bottom spin valves. DRs reached 4.22 /spl Omega//Sq at the Cu thickness of 10 /spl Aring/ compared with 3.09 /spl Omega//Sq at the Cu thickness of 18 /spl Aring/. They show that the temperature dependence of MR ratio and DRs up to 200/spl deg/C for underlayer55/spl Aring//NiFe10/spl Aring//IrMn70 /spl Aring//CoFe20/spl Aring//Ru4/spl Aring//CoFe23/spl Aring//Cu10.4/spl Aring//CoFe20/spl Aring//NiFe10/spl Aring//Ta50/spl Aring/ films. MR ratio decreased from 13.0% to 7.3% and DRs from 3.16 /spl Omega//Sq to 2.25 /spl Omega//Sq as the temperature increased from 25/spl deg/C to 200/spl deg/C. Thus, these bottom spin valves having very thin Cu spacers exibit high MR ratio, high DRs and excellent temperature characteristics.