Exchange Coupling between CrMn-Based Antiferromagnetic Films and NiFe Films.

We investigated the exchange coupling between ferromagnetic Ni81Fe19 and antiferromagnetic CrMn alloy films. The exchange coupling field (HEX) of CrMn alloy film, with 40 nm Ni81Fe19 film is 5 Oe at 50 at% Mn content. If several at% of Cu, Pt, Pd, and Rh are added to Cr50Mn50 films, HEX is approximately 16 Oe. In the case of Pt addition, HEX increases with increasing Pt content and saturates at more than 5 at% Pt. CrMnPt (110) films with body-centered cubic structures are formed on NiFe (111) films. With increasing sputtering Ar gas pressure, both HEX and the blocking temperature (TB) of Ni81Fe19/Cr46Mn46Pt8 increase. At an Ar gas pressure of 15 mTorr, HEx and TB are 15 Oe and 380°C, respectively. HEX of Ni81Fe19/Cr46Mn46Pt8 films decreases with decreasing CrMnPt film thickness, and at least 30 nm thickness is required in order to maintain a positive value of HEX. From these results, we conclude that it may be possible to use antiferromagnetic CrMnPt film in MR heads and spin-valve films.