Exchange bias and spin-valve giant magnetoresistance in multilayers with Mn-17 mol%Ir-2 mol%Pt antiferromagnetic layer

We fabricated bottom spin valves (SV) films using Mn-17 mol%Ir-2 mol%Pt antiferromagnetic material. A bottom SV composing of Ta/Ni-20 mol%Fe seed layer shows an improved exchange field (H_ex). The high H_ex of about 17.4 kA/m was obtained in Si(100)Ta 3 nm/NiFe 3 nm/Mn-17 mol%Ir-2 mol%Pt 7 nm/Co-10 mol%Fe 1 nm/NiFe 5 nm/Ta exchange biasing layer. The giant magnetoresistance (GMR) and the thermal stability of bottom SVs were evaluated by comparing with a top SV. Bottom SV showed the higher GMR ratio of about 5.2% than a top SV with same thick ferromagnetic layer. It seems that a large short circuit effect of conductance in a free layer of a bottom spin valve. In order to improve thermal stability of a bottom SV, we inserted the synthetic antiferromagnetically coupled pinned layers (Co-Fe/Ru/Co-Fe) between the Mn-17 mol%Ir-2 mol%Pt and Cu layers. Thus, the enhanced thermal stability of H_ex can be obtained in bottom synthetic SVs.