Effect of Ta buffer and NiFe seed layers on pulsed-DC magnetron sputtered Ir20Mn80/Co90Fe10 exchange bias

Abstract

A systematic investigation has been done on the correlation between texture, grain size evolution and magnetic properties in Ta/Ni 81Fe19/Ir20Mn80/Co 90Fe10/Ta exchange bias in dependence of Ta buffer and NiFe seed layer thickness in the range of 210 nm, deposited by pulsed DC magnetron sputtering technique. A strong dependence of <1 1 1> texture on the Ta/NiFe thicknesses was found, where the reducing and increasing texture was correlated with exchange bias field and unidirectional anisotropy energy constant at both NiFe/IrMn and IrMn/CoFe interfaces. However, a direct correlation between average grain size in IrMn and Hex and H c was not observed. L12 phase IrMn3 could be formed by thickness optimization of Ta/NiFe layers by deposition at room temperature, for which the maximum exchange coupling parameters were achieved. We conclude finally that the coercivity is mainly influenced by texture induced interfacial effects at NiFe/IrMn/CoFe interfaces developing with Ta/NiFe thicknesses.