The Study on The Modulation of The Exchange Bias in The Inverted (Co/Pt)n/Co/IrMn Structure By The Current Induced Joule Heating

The exchange bias has a crucial influence on the key performance parameters of magneroresistive sensors, which have wide applications in many fields. This paper presents a method that uses the Joule heating effect together with the help of a magnetic field to modulate the exchange bias in magnetic multilayers. By this method, we systematically modulate the in-plane exchange bias field (H_eb) in the inverted (Co/Pt)_n/Co/IrMn structure (n + 1 is the repetition of the Co layers), here the thickness of the Pt layers is smaller than that of the Co layers. In these inverted structures, the H_eb can be continuously modulated by changing the amplitude of a pulse current I_DC (an in-plane magnetic field H_p) after fixing a H_p (I_DC). In more detail, the H_eb deceases gradually by increasing the I_DC and its polarity of the H_eb can be reversed finally, which would not disappear even under a large I_DC. Furthermore, if both the amplitude and direction of I_DC (H_p) are changed while fixing a H_p (I_DC), a reversal of H_eb can be realized from positive (negative) to negative (positive) direction under a large I_DC. From here, one may find the modulation of the exchange bias in our text is totally different from the normal case people think, where the H_eb becomes zero under an enough large I_DC due to the pure heating effect. So, we believe these results obtained above show that our method can modulate in situ the linear magnetic field range and sensitivity, which may be important to guide for optimizing the performance parameters of magneroresistive sensors.