Seed layer characterization for PtMn bottom spin-filter spin valves

Abstract

The effect of seed layers on the giant magnetoresistance (GMR) response of bottom spin-filter spin valves (SFSVs) of the structure (seed layer)/PtMn/CoFe/Cu/CoFe/NiFe/Cu/Ta have been studied in detail. Four types of seed layers, NiFeCr, Ta/NiFeCr, NiFeCr/NiFe, and Ta/NiFe were used. The GMR response has been found to be very sensitive to the type and the thickness of the seed layers, which determine the crystallographic quality of the films and the degree of the fcc to fct phase transformation of the PtMn crystals in the films. Among the four, Ta/NiFeCr and NiFeCr/NiFe seed layers give the optimal GMR performance at a NiFeCr layer thickness of about 40–45 Å.