Exchange Bias Characteristics in Specular Spin Valve System With Embedded (Co–Fe)/Cr Nano-Oxide-Layer in Pinned Ferromagnetic Layer

The insertion of a nano-oxide-layer (NOL) into a spin valve system is well known to be very effective in enhancing the magnetoresistance ratio at both of current-in-plane (CIP) and current-perpendicular-to-plane (CPP) geometries. Recently, a clear NOL pinning assist effect is reported to be observed in the low temperature range below ~150 K by using the magnetic field cooling method from room temperature (R.T.) in the Co_0.9Fe_0.1 pin-NOL, wherein the NaCl-type CoO-FeO antiferromagnetic component exists. In this paper, the NOL pinning assist effect in a specular spin valve system with (Co-Fe)/Cr pin-NOL is presented. An ultra-thin Cr layer deposit on the Co-Fe layer before oxidation leads to increase the exchange bias field still more with the increment of the blocking temperature (T_B)of the (Co-Fe)-NOL biasing in the low temperature range below R.T. and to fully exploit the superior pinning properties of the metallic antiferromagnet (Ir-Mn) at R.T. in the Co-rich region. The effect of ultra-thin Cr layer on the NOL exchange bias is considered from the aspect of the complicated oxide formation and its magnetism.