Controllable positive exchange bias via redox-driven oxygen migration

Abstract

Ionic transport in metal/oxide heterostructures offers a highly effective means to tailor material properties via modification of the interfacial characteristics. However, direct observation of ionic motion under buried interfaces and demonstration of its correlation with physical properties has been challenging. Using the strong oxygen affinity of gadolinium, we design a model system of GdxFe1−x/NiCoO bilayer films, where the oxygen migration is observed and manifested in a controlled positive exchange bias over a relatively small cooling field range. The exchange bias characteristics are shown to be the result of an interfacial layer of elemental nickel and cobalt, a few nanometres in thickness, whose moments are larger than expected from uncompensated NiCoO moments. This interface layer is attributed to a redox-driven oxygen migration from NiCoO to the gadolinium, during growth or soon after. These results demonstrate an effective path to tailoring the interfacial characteristics and interlayer exchange coupling in metal/oxide heterostructures.

Emergence of Multispinterface and Antiferromagnetic Molecular Exchange Bias via Molecular Stacking on a Ferromagnetic Film

“…These results indicate that the ferromagnetic Fe and van der Waals stacking of antiferromagnetic CoOEP layers are antiferromagnetically coupled at their interface . Note that antiferromagnetic coupled inorganic heterostructures have also shown disentangled ferromagnetic interfaces . Figure c,d represent schematic spin configurations of the Fe/CoOEP system for low H FC and high H FC cases, respectively.…”

“…In this wise, ferromagnetic Fe film could be the best candidate to accommodate the antiferromagnetic interfacial interaction as its surface could be partially oxidized. This unusual antiferromagnetic interface coupling at a ferromagnet/antiferromagnet bilayer has been extensively studied in an inorganic system exhibiting inversion of exchange bias with controllable anisotropy, but not realized in an organic system yet.…”

Electrical Control of Perpendicular Magnetic Anisotropy and Spin‐Orbit Torque‐Induced Magnetization Switching

“…Recently, it has been found that the perpendicular exchange coupling across the ferromagnetic/antiferromagnetic interface can influence both the coercivity and the PMA of a ferromagnetic sublayer in permalloy/CoO,22 CoPt/CoO,23 Co/CoO,24,25 and Fe/Mn26 systems. This provides a powerful platform for tailoring PMA as well as realizing emergent voltage‐controlled functionalities 27,28. In this work, interfacial exchange coupling of magnetic moments between ferromagnetic metal and antiferromagnetic oxides is used as an extra source to stabilize the perpendicular magnetic anisotropy.…”

Manipulating exchange bias using all-optical helicity-dependent switching

“…The orientation of the FM layer magnetization sets the orientation of the interfacial AFM spins because of the interface exchange coupling between the two layers. Other ways of controlling and manipulating exchange bias have been very recently * Corresponding author: Stephane.mangin@univ-lorraine.fr investigated relying on ionic motion at interfaces [18] or modifying the crystal structure [14].…”

“…The fundamental mechanism explaining exchange bias has been discussed extensively [19][20][21][22] but remains a topic of high interest [23,18]. Ultrafast optical excitations of an AFM/FM bilayer have been used to probe the interfacial interaction between the AFM and the FM layers, and interesting fast magnetization dynamics have already been observed [24][25][26].…”