Four generations of magnetic sensing technology

n  1st Generation: Hall Effect Sensor

n   2nd Generation: AMR (Anisotropic Magneto Resistance) Sensor

n   3rd Generation: GMR (Giant Magneto Resistance) Sensor

n  4th Generation: TMR (Tunneling Magneto Resistance) Sensor

Hall Working Principle

n  Electrons moving in a magnetic field are deflected by the Lorentz Force in a direction transverse to both the motion and the magnetic field.  Charges deflected to the edges of a device create a transverse electric field known as the “Hall Field”.

n  Senses the magnetic field in the direction perpendicular to the sensor plane

AMR Working Principle

n  Single ferromagnetic layer

n  Magnetization parallel to magnetic field

n  1～3% △R/R

n  Operates with current at 45° angle to magnetization

n  Current flowing in the film plane

n  Narrow magnetic field operating range

GMR Working Principle

n  Resistance depends on the film interface spintronic scattering

n  Most electron scattering is not spintronic

n  At room temperature, maximum GMR ratio of resistance change is （△R/R）<20%

TMR Working Principle

n  TMR effect uses the electron spin density in a magnetic tunnel junction (two magnetic layers separated by a thin Insulating layer); 

n  Spintronic electrons conduct through the insulating layer MgO (Magnesium oxide) according to the quantum tunneling effect.   When the magnetization directions of the two magnetic layers are parallel, the tunneling current is greatest (low resistance).  When they are antiparallel, the tunneling is smallest (high resistance).  

n  At room temperature, the maximum TMR ratio of resistance change is （△R/R）up to 500% or more.  

TMR Excellence

n  Low Power Consumption

n  High Sensitivity / High Resolution

n  Wide Magnetic Field Operating Range

n  Large Temperature Operating Range

n  High Frequency Response, >GHz