Effects of underlayer on one-directional anisotropy in spin-valve films without any antiferromagnetic layers

The magnetoresistive (MR) characteristics of spin-valve films with no antiferromagnetic layer were investigated. The films were deposited with various underlayer materials and the one-directional anisotropy in MR curves of the film with Ta underlayer turned out very strong anisotropy compared with that of other materials. It seemed that the strong one-directional anisotropy was caused by increase of coercivity and magnetic anisotropy induced in the pinned layer by external dc magnetic field during deposition. The calculated MR curves by using a torque equation clarified a relation between the magnetic characteristics of the pinned layer and the one-directional anisotropy in measured MR curves.