Canting of exchange coupling direction in spin valve with various pinned layers

One of the problems in spin valve (SV) is the thermal stability of exchange coupling between the pinned magnetic layer and the antiferromagnetic (AFM) layer. During operating in actual hard disk drives, the pinned direction tends to cant toward the longitudinal hard magnet direction and as a result, the output voltage drops. In this study we examine the amount of the cant by the heat and field in SV which used different pinned layer material. The sample we used is Ta(5)/NiFe(9)/ Co(1)/Cu(2.7)/pinned layer/AFM/Ta(5) unit nanometers. The pinned layer is three kinds-Co(2), Co(1)/NiFe(1.7), NiFe(3.5), and AFM is two kinds of Ru₃Rh₁₅Mn(12 nm), Ru₃Rh₁₅Mn(S nm). The pinned-Co-SV has a larger increase of canting degree than the pinned-Co/NiFe-SV and the pinned-NiFe-SV. The longer the SV is exposed to heat and magnetic field, the more the cant increases. It is likely due to the change of the local pinned direction which in turn may be due to the aftereffect in the minute AFM grains during the heating process.