Method for Providing a Magnetic Sensor with a Biasing Spin-Orbit Effective FieldTechnology #2016-233
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Driven by the hard disk industry, various types of thin film magnetic sensors have been developed in the last 2 decades. These include anisotropic magnetoresistance (AMR) sensor, giant magnetoresistance (GMR) sensor, magnetic tunnel junctions (MTJ) sensor and planar Hall effect (PHE) sensor.
The biasing schemes needed for these sensors significantly increases the number of process steps during sensor manufacturing. Moreover, the mostly commonly used biasing scheme, patterned longitudinal bias often results in non-uniform bias field in the sensor area.
NUS researchers invented a novel application of Spin Orbit Torque (SOT) in magnetic sensor. A new type of magnetic multilayers is developed and is based on ultrathin Pt and FeMn layers. By controlling the Pt and FeMn layer thickness, it is possible to achieve both ferromagnetic properties and SOT effect in [Pt(t1)/FeMn(t2)]n multilayers above room temperature, with t1 and t2 in the range of 0.4 to 0.8 and 0.2 to 1 nm respectively.
Fig. 1 depicts a PHE sensor where the sensor element has an elliptic shape. Current flows between the two electrodes I+ and I- and PHE signal is detected across the two voltage probes V+ and V-. The sensing layer in this instance is a multilayer with a structure of SiO2/[Pt(0.4)/FeMn(0.6)]6/Pt(1). Spin current is generated by the Pt layers which is absorbed by the neighboring FeMn layers to generate SOT.
• Magnetic sensor with SOT-biasing to achieve high-linearity and high-sensitivity.
• Significantly simplified design which eliminates the conventional bias scheme.
• Magnetic sensing working point is set by SOT effective field.
• Especially useful for detection of low-magnetic field, e.g. in bio-sensing.
• Patent pending.
For more information, contact:
NUS Industry Liaison Office, HJ Chen
:+65 6601 2814
Ref : 2016-196