Cu thickness dependence of interlayer coupling for free layer on NiMn alloy-pinned spin valve films

Abstract

Annealing cycle number and nonmagnetic layer thickness dependences of interlayer coupling field (Hint) and coercivity (H-cf) of free magnetic layer on NiMn alloy-pinned spin valve films (SVF), glass/Ni81Fe19(70 Angstrom)/Co(10 Angstrom)/Cu(t Angstrom)/Co(15Angstrom)/Ni81Fe19(35 Angstrom)/Ni25Mn75(250 Angstrom)/Ta(50 Angstrom) prepared by magnetron sputtering, were investigated. At a Cu thickness of SVF of 35 A and peak exchange coupling field (H-ex) of 620 Oe, coercivity H-c = 280 Oe and MR ratio = 2.5%. For every SVF H-inf and H-cf increased up to stabilized values with the increase of annealing cycle number up to 15, which were 120 Oe for H-inf and 75 Oe for H-cf. The increase of H-cf with the annealing cycle number seems to be caused by the effective reduction of Cu layer thickness due to the increase of interfacial mixing of Cu layer and Co layer. The effect of interfacial mixing is analysed to be increased or weakend when the Cu layer becomes thinner or thicker than the Cu layer thickness of 35 Angstrom, respectively.