Scalable Toggle Read Sensor

A read sensor working in the toggle mode is presented. The free layer comprises a balanced synthetic-antiferromagnetic (SAF) multilayer. The magnetization of the free SAF layer is perpendicular to the air-bearing surface (ABS) when bias field is applied in the direction of the ABS. The magnetization of the reference layer is fixed to be parallel to the ABS instead of perpendicular as is the conventional case. The sensitivity of the toggle read sensor (for small track width) improves significantly compared to the conventional abutted junction bias type. For a toggle sensor with long height structure, performance in both the sensitivity and linearity has also been improved because increased sensor height can be used for the lower bias field. The lower bias field is also compatible with the small gap structure of an in-stack bias scheme. Simulation results also show that the thermal magnetic noise in the toggle sensor is much smaller than that in the conventional biased sensor. Experimental results for both the current-in-plane (CIP) and tunneling-magneto-resistive (TMR) sensors with toggle mode are consistent with our calculation results