The Effects of Ruthenium and Grain Size on Spin Valves With Ultra Thin Antiferromagnetic Pinning Layers

Improvements in exchange-biased spin valves have come from control of the grain size and the addition of a ruthenium layer. In this work the GMR ratio, the exchange field and blocking temperature for three sets of spin valves with varying IrMn thickness were measured. Two sets of samples with grain sizes of 10 nm, and one with a grain size of 30 nm were studied. One of the 10 nm grain size sets has a Ru layer separating the antiferromagnet from the Ta capping layer. The GMR ratio at 5 K depends on the grain size, but shows no dependence on the presence of the Ru layer, with larger grain samples having a higher GMR ratio. The exchange fields at 5 K are independent of grain size. However, the samples with the Ru layer show a higher exchange field at 5 K than those without. The blocking temperature for the small grain sets with and without Ru correlate very well with the exchange field. Ta in contact with the IrMn causes a magnetically "dead" region