Planar Hall Resistance Sensor With Improved Thermal Stability

Abstract

High thermal stability of the planar Hall resistance (PHR) signal in magnetic sensors, configured as a cross-junction and as a Wheatstone bridge, has been demonstrated. The thermal drift of the PHR signal, which is proportional to the PHR offset at zero field, is few orders of magnitude less than the thermal drift of the anisotropic magnetoresistance signal. The thermal drift of the PHR originates from two independent components: baseline drift and signal amplitude drift. The temperature coefficient of baseline drift, normalized by zero-field offset, is similar to the temperature coefficient of resistance. This makes it possible to characterize drift in any temperature range by a single measurement of PHR under ambient conditions. Signal amplitude drift is shown to be dependent on a sensor's geometry, and becomes higher with a reduction of the width of the current path. The temperature coefficients of baseline drift and signal amplitude drift are of opposite sign. The possibility of mutual compensation of signal amplitude drift and baseline drift by a slight imbalance in a bridge-type sensor is demonstrated. © 2010-2012 IEEE.