Reduction of the Switching Field of TMR Devices.

Two types of laminated structures for free layers were investigated to avoid the increase in the switching field of the free layer caused by the reduction of the size of the TMR element. Laminated free layers of NiFe(5)/Ru(0.7)/NiFe(3) and NiFe(4)/Ta(3)/NiFe(4) showed a lower switching field than a single free layer of NiFe(8). The low switching field of the synthetic free layer is due to the decrease in the net moment, which results in a decrease of the demagnetizing field. In the case of the NiFe(4)/Ta(3)/NiFe(4) free layer, there is a possibility that magnetostatic coupling plays an important role in the decrease in the demagnetizing field.