IrMn based spin-filter spin-valves

Abstract

As recording densities increase, the sense layer (free layer) thickness in a recording head (whether spin-valve or otherwise) must also decrease so that the sense layer can be effectively saturated by the transitions on the media. However, in a traditional spin-valve structure, reducing the sense layer (free layer) thickness below ∼50 Å results in a rapid reduction in ΔR/R. One of the solutions for this is the spin-filter spin-valve, having a free layer composed of a very thin magnetic layer and an adjacent thin enhancing conduction layer. The advantage of the spin-filter spin-valve is high ΔR/R and easy control of the bias point while keeping the free layer very thin (10–30 Å). The present work reports the results on sputtered IrMn top and bottom spin-filter spin-valves. The data clearly show that ΔR/R has been significantly improved when reducing the free layer CoFe down to 10 Å. ΔR/R>8.0% remains for free layer thickness between 10 and 20 Å using a Cu enhancing layer, while ΔR/R decreased rapidly to 4.0% with no Cu enhancing layer for the same free layer thickness range. An optimized ΔR/R of ∼10% was obtained for an enhancing layer of tCu∼13 Å, as a result of the balance between the increase in electron mean free path difference and current shunting through the very conducting enhancement layer. It was also found that the softness of the CoFe free layer was improved when sandwiched by Cu layers, showing similar soft properties and magnetostriction to conventional free layers. Such a soft, thin CoFe free layer is particularly attractive for high density (30–50 Gb/in2) read sensor applications.