Abrupt suppression of the exchange bias across a non-magnetic insulator spacer

Abstract

This paper reports results obtained on exchange-biased IrMn/Al2O3/Co films deposited by magnetron sputtering, where the thickness of the non-magnetic insulator layer, tAl2O3, was varied. Ferromagnetic resonance and static magnetization measurements were used to study the exchange interaction between the antiferromagnet (IrMn) and ferromagnet (Co) layers. X-ray diffractometry and x-ray reflectometry as well as high-resolution transmission electron microscopy were employed for structural characterization of the films. It was found that the IrMn/Co exchange coupling decreases very abruptly with tAl2O3 being the exponential decay length at least four times smaller than the values previously reported for exchange-bias systems. Such a rapid suppression of the coupling is explained in terms of the prompt loss of the direct contact between the antiferromagnet and the ferromagnet with tAl2O3.

Negative rotatable anisotropy in IrMn/Cr/Co thin films

“…8,9,28 The symbols in Fig. 5 represent the experimentally obtained H res (φ H ) for the films with t Cr 2.0 nm, where the lines give the corresponding best-fitting curves calculated through the AF domain-wall-formation model 29,30 with the help of a previously derived expression 31 for H res (φ H ).…”

“…The steeper rise of H res as compared to H RA for high t Cr might be due to the better separation between the Co and Cr phases, given that the value of H res for t Cr = 3 nm is very close to that of an uncoupled Co layer of an analogous system with nonmagnetic insulator SL. 9 We also performed a series of magnetization loop simulations. However, the particularity of the EB system studied, i.e., H U several times smaller than |H RA | and the negative sign of the latter estimated from the FMR angular variations, does not allow the prompt use of models that assume constant RA when simulating complete magnetization hysteresis cycles 13 if the anisotropy parameters from the FMR fittings are to be used.…”

“…[1][2][3][4] One of the contentious topics related to the effect concerns the range of the antiferromagnet/ferromagnet (AF/FM) interactions. While nearest-neighbor coupling is normally reported, [5][6][7][8][9] long-range contributions to EB across a spacer layer (SL) have also been asserted. 10 The coupling strength has been observed to decay exponentially in AF/SL/FM structures with metal SLs.…”

Remanence plots technique extended to exchange bias systems

“…The maximum value of Dm dc r decreases and its position shifts towards low-field values when t Cu is increased confirming that the effective FM/AF exchange coupling decreases as the thickness of the spacer is increased. 23,24 The same holds for the asymmetries in the hysteresis loop's shape and in the magnetization reversal, i.e., Dm dc r versus t Cu indicates that the FM is practically uncoupled for t Cu ! 1:0 nm.…”

Exchange bias in epitaxially grown CoO/MgO/Fe/Ag(001)

“…For metallic spacer layer, the exchange bias is found to exhibit an oscillatory, non-monotonic, or an exponential decay with the spacer layer thickness [15,16,17,18,19,20]. For insulating spacer layer, the exchange bias has only been reported so far to decay exponentially with the spacer layer thickness [ 21 ]. In this paper, we report an experimental study of epitaxially grown CoO/MgO/Fe/Ag(001) single crystalline thin films.…”