IrMn based spin-filter spin-valves

As recording densities increase, the sense layer (free layer) thickness in a recording head (whether spin-valve or otherwise) must also decrease so th at the sense layer can be effectively saturated by the transitions on the m edia. However, in a traditional spin-valve structure, reducing the sense la yer (free layer) thickness below similar to 50 Angstrom results in a rapid reduction in Delta R/R. One of the solutions for this is the spin-filter sp in-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 Delta R/R and easy control of the bias point while keep ing the free layer very thin (10-30 Angstrom). The present work reports the results on sputtered IrMn top and bottom spin-filter spin-valves. The data clearly show that Delta R/R has been significantly improved when reducing the free layer CoFe down to 10 Angstrom. Delta R/R > 8.0% remains for free layer thickness between 10 and 20 Angstrom using a Cu enhancing layer, whil e Delta R/R decreased rapidly to 4.0% with no Cu enhancing layer for the sa me free layer thickness range. An optimized Delta R/R of similar to 10% was obtained for an enhancing layer of t(Cu)similar to 13 Angstrom, as a resul t 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 sand wiched by Cu layers, showing similar soft properties and magnetostriction t o conventional free layers. Such a soft, thin CoFe free layer is particular ly attractive for high density (30-50 Gb/in(2)) read sensor applications. ( C) 2000 American Institute of Physics. [S0021-8979(00)74108-9].