Influence of Base Pressure on FeMn Exchange Biased Spin-Valve Films

Spin-valve films of structure NiFeCo/Co/Cu/NiFeCo(Co)/FeMn/Cu were deposited on Si substrates by DC planetary magnetron sputtering techniques. The influence of base pressure, P{sub b}, on spin-valve properties was studied by varying P{sub b} over two decades from 3 x 10{sup -8} to 7 x 10{sup -6} Torr. The GMR ratio show a slight increase with increasing P{sub b} until a large decrease occurs at P{sub b} > 3.3 x 10{sup -6} Torr. Exchange bias field and blocking temperature remain constant in the base pressure range between 3 x 10{sup -8} and 5 x 10{sup -7} Torr before a large reduction begins. An upper bound base pressure, {sup u}P{sub b} {approx} 5 x 10{sup -7} Torr, is noted from the data, above which significant performance modification begins. The degradation in exchange bias field and blocking temperature, in particular, in spin-valve films using a NiFeCo pinned layer, is the result of deterioration in the crystallographic texture and can be understood due to the contamination both at the ferromagnetic/antiferromagnetic interface and in the bulk of FeMn layer