Uncompensated spins in trilayer CoFe/IrMn/NiFe exchange bias: soft x-ray resonant magnetic scattering study

Abstract

We investigated an uncompensated (UC) layer in a magnetic trilayer CoFe/IrMn/NiFe using soft x- ray resonant magnetic reflectivity. Under a carefully controlled magnetic field, we resolved two UC spins in the single antiferromagnetic (AFM) layer. We found that the unpinned spins formed at both sides within the 50 angstrom thick IrMn AFM layer: t(UC1) = 17.8 angstrom for CoFe/IrMn((1)) and t(UC2) = 6.4 angstrom for IrMn((2))/NiFe. Moreover, we noted their different blocking temperatures, namely T(B) = 500 K at the UC1 layer and 470 K at the UC2 layer. There might be no noticeable magnetic interaction of the pinned spins of the two separated UC layers. Our results verify the distinct spatial separation of the two UC layers, despite the limited thickness of the single AFM layer.