Recently, magnetic tunnel junctions with perpendicular magnetized electrodes combined with exchange bias films have attracted large interest. In this paper we examine the tunnel magnetoresistance of Ta/Pd/IrMn/Co-Fe/Ta/Co-Fe-B/MgO/Co-Fe-B/capping/Pd magnetic tunnel junctions in dependence on the capping layer, i.e., Hf or Ta. In these stacks perpendicular exchange bias fields of -500\,Oe along with perpendicular magnetic anisotropy are combined. A tunnel magnetoresistance of (47.2±1.4)% for the Hf-capped sample was determined compared to the Ta one (42.6±0.7)% at room temperature. Interestingly, this observation is correlated to the higher boron absorption of Hf compared to Ta which prevents the suppression of Δ1 channel and leads to higher tunnel magnetoresistance values. Furthermore, the temperature dependent coercivities of the soft electrodes of both samples are mainly described by the Stoner-Wohlfarth model including thermal fluctuations. Slight deviations at low temperatures can be attributed to a torque on the soft electrode that is generated by the pinned magnetic layer system.
@article{arxiv.1709.02607,
title = {Tunneling magnetoresistance of perpendicular CoFeB-based junctions with exchange bias},
author = {Orestis Manos and Alexander Böhnke and Panagiota Bougiatioti and Robin Klett and Karsten Rott and Alessia Niesen and Jan-Michael Schmalhorst and Günter Reiss},
journal= {arXiv preprint arXiv:1709.02607},
year = {2017}
}