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 (<i>H</i><sub>eb</sub>) in the inverted (Co/Pt)<sub>n</sub>/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 <i>H</i><sub>eb</sub> can be continuously modulated by changing the amplitude of a pulse current <i>I</i><sub>DC</sub> (an in-plane magnetic field <i>H</i><sub>p</sub>) after fixing a <i>H</i><sub>p</sub> (<i>I</i><sub>DC</sub>). In more detail, the <i>H</i><sub>eb</sub> deceases gradually by increasing the <i>I</i><sub>DC</sub> and its polarity of the <i>H</i><sub>eb</sub> can be reversed finally, which would not disappear even under a large <i>I</i><sub>DC</sub>. Furthermore, if both the amplitude and direction of <i>I</i><sub>DC</sub> (<i>H</i><sub>p</sub>) are changed while fixing a <i>H</i><sub>p</sub> (<i>I</i><sub>DC</sub>), a reversal of <i>H</i><sub>eb</sub> can be realized from positive (negative) to negative (positive) direction under a large <i>I</i><sub>DC</sub>. 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 <i>H</i><sub>eb</sub> becomes zero under an enough large <i>I</i><sub>DC</sub> 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.