Effects of Nb buffer layer on superconducting and magnetic behavior of IrMn/NiFe/Nb/NiFe spin-valves

IrMn/NiFe/Nb/NiFe spin-valves have been grown on Ta and Nb buffer layers. A reduction of the superconducting transition temperature (TC) of the Nb spacer layer has been observed by transport measurements when Nb is used as buffer layer. Magnetic hysteresis measurements and X-ray diffraction experiments further indicated that the Nb buffer layer can cause a change of the exchange bias field presumably due to higher degree of (200) preferred orientation in IrMn promoted by the buffer layer. The reduction of TC of the Nb spacer in these spin-valves is attributed to the stray fields from domain walls due to domain rearrangement in NiFe.