Tuning of exchange bias effect in Co/CoO by molecular layers

Molecular spintronics aims to manipulate spins by a combination of molecules and magnetic substrate. Unexpected magnetic configurations have been identified at the interface between molecules and magnetic surface giving rise to the so called Spinterface. This opens the possibility to implement the functionality of devices exploiting the ability of certain molecules to respond to external stimuli and then to modify the properties of the magnetic layer. In this work, we adopted an innovative approach investigating the effects of spinterface formation with antiferromagnetic (AFM) thin films. The use of AFM materials has many advantages, such as robustness against magnetic fields or the ability to excite spin waves in the THz range, allowing the construction of ultra-fast and zero power consumption devices. We investigated the effects of two molecules, Fullerene and Gallium-quinoline, coupled with an AFM material, Cobalt Oxide (CoO). Detecting AFM materials is challenging due to their magnetic neutrality, so we coupled CoO to a ferromagnetic Cobalt (Co) layer generating exchange bias effect. The effects of the AFM-organic coupling are then detected through changes induced in the CoO-Co exchange bias coupling. With this aim, we performed both static and dynamic characterization by MOKE techniques. The deposition of molecules on the CoO layer affects the magnetic response of Co, evidenced by an increase of exchange bias coupling. The increase in blocking temperature suggests an enhanced stability of the AFM state. In terms of magnetization dynamics, we detected larger precession frequencies of Co magnetic moments in samples coated with molecules associated to larger anisotropy fields. Our investigations confirm the formation of “spinterface” between CoO and organic molecules, resulting in an enhancement of stability of AFM grains. Our results contribute to the development of innovative strategies in the field of molecular spintronics.