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IrMn Bottom Spin Valves With Improved Signal Using Si Underlayers

IP.com Disclosure Number: IPCOM000013487D
Original Publication Date: 2002-May-03
Included in the Prior Art Database: 2003-Jun-18

Publishing Venue

IBM

Abstract

Disclosed is the application of Silicon (Si) underlayers for use in spin valves. Si underlayers increase the ∆ R/R from 7.1% to 8.8% in top IrMn spin valves, and 6% to 7.8% for bottom IrMn spin valves. This is accompanied by a decrease in sheet resistance and the exchange anisotropy field, Hex. These results suggest that films grown on Si have larger grains than those with other seed layers. Figure 1 shows data from IrMn “top” spin valves grown on Si underlayers. The structure was: t Si/40 NiFe/5 CoFe/25 Cu/30 CoFe/80 IrMn/30 Ru. With 10Å Si as an underlayer the properties are very similar to control samples with Ru as the underlayer: ∆ R/R is 7.1% and Hex is 392 Oe. For tSi>20 Å ∆ R/R is significantly higher at 8.8%. Concurrently, Hex drops to 224 Oe and the sheet resistance drops from 21.8 to 18.2 Ohm/square. This would suggest that the films grown on Si have a larger grain diameter. This would lead to lower R and higher ∆ R/R due to decreased grain boundary scattering. Also, this would explain the lower Hex. Hex typically follows a 1/a relationship where a is the average area of an antiferromagnetic grain. This is the case where NiFeCr/NiFe underlayers are used[2]. 9.0 500