Exchange bias effect of current Joule thermally modulated inverted vertical (Co/Pt) n/Co/IrMn nanomultilayers

Abstract

The exchange bias has a crucial influence on the key performance parameters of magneroresistive sensor, which has wide applications in many fields. This paper presents a method that uses the Joule heating effect combined with 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>_eb) in the inverted (Co/Pt)_<i>n</i>/Co/IrMn structure (<i>n</i> + 1 is the repetition of the Co layers), here the thickness of the Pt layer is smaller than that of the Co layer. In these inverted structures, the <i>H</i>_eb can be continuously modulated by changing the amplitude of a pulse current <i>I</i>_DC (an in-plane magnetic field <i>H</i>_p) after fixing an <i>H</i>_p (<i>I</i>_DC). In more detail, the <i>H</i>_eb deceases gradually by increasing the <i>I</i>_DC and its polarity of the <i>H</i>_eb can be reversed finally, which will not disappear even under a large <i>I</i>_DC. Furthermore, if both the amplitude and direction of <i>I</i>_DC (<i>H</i>_p) are changed, with a <i>H</i>_p (<i>I</i>_DC) fixed, a reversal of <i>H</i>_eb can be realized from positive (negative) to negative (positive) direction under a large <i>I</i>_DC. From here, one may find that the modulation of the exchange bias in our text is totally different from the normal case one thinks, where the <i>H</i>_eb becomes zero under a large enough <i>I</i>_DC due to the pure heating effect. Therefore, we believe that the above results show that our method can modulate in situ the linear field range and sensitivity, which has important significance in guiding the optimization of the performance parameters of magneroresistive sensors.