Influence of crystal structure and oxygen content on exchange-coupling properties of IrMn/CoFe spin-valve films

Investigations were made into the relationship between the exchange-coupling properties and the IrMn crystal grain size for CoFe/IrMn spin valves. The IrMn crystal grain size increased with increasing thickness and decreasing oxygen content of the IrMn layer. The increase in the IrMn grain size resulted in a higher blocking temperature (T-B) but a lower unidirectional anisotropy field (H-UA). This opposite dependence of T-B and H-UA on the IrMn grain size is different from those of other antiferromagnetic films such as FeMn, NiMn, and CrMnPt. An H-UA of 400 Oe at room temperature and a T-B of 300 degrees C are obtained for CoFe (2 nm)/IrMn (10 nm) spin valves by controlling the oxygen content of the IrMn layer. (C) 1999 American Institute of Physics. [S0003-6951(99)01649-6].