We report an enhancement of the average blocking temperature < T-B > in IrMn/CoFe exchange bias systems due to an increase in the anisotropy constant of the IrMn. This is related to a (111) texture of IrMn parallel to the interface. Si < 100 >/Seed (5 nm)/IrMn (10 nm)/CoFe (3 nm)/Ta (10 nm) were prepared by dc sputtering. Cu, Ru, and NiCr seed layers were used. X-ray diffraction studies involving both theta/2 theta and grazing incidence scans revealed a strong (111) texture of the IrMn parallel to the interface for the samples with a NiCr seed layer. Cu and Ru seed layers did not cause a marked texture. Thermal activation measurements found an enhancement of the average blocking temperature from 367 K for the sample with Cu seed layer to 477 K for the sample with a NiCr seed. The anisotropy constant was found to increase from (2.8 +/- 0.2) x 10(6) erg/cm(3) for the sample with a Cu seed layer to (3.3 +/- 0.4) x 10(7) erg/cm(3) for the sample with a NiCr seed layer. We find that the increase in the anisotropy constant leads to an enhanced blocking temperature.
- exchange bias
- thermal activation