Study counters previous observations of a spinterface effect in spintronic technology

An emerging field within nanoelectronic devices, spintronic technology relies on magnetic layers to transmit spin-polarized electrons. Many such devices, including magnetic read heads, MRAMS, and most kinds of magnetic sensors, require a physical effect — exchange bias — whereby the hard magnetization of one of the magnetic thin films causes a shift in the soft magnetization curve of the ferromagnetic film.

For two decades, exchange bias has been accomplished with metallic and oxide components. Recent research has focused on implementing the process with organic components in order to build environmentally-friendly, mechanically soft, and foldable devices in the future.

Avedissian et al. investigated previous observations in hybrid systems where a metallic ferromagnet is exchange biased by an organic film. This phenomenon was believed to be a spinterface effect. However, their study showed the molecular exchange bias in hybrid systems to be caused by partial oxidation of the soft ferromagnetic film rather than a spinterface effect by the molecule/inorganic hybrid interface.

“Such hybrid devices are very difficult to encapsulate and those not adequately protected from room atmosphere ingress did indeed show exchange bias,” said co-author Christian Meny. “It wasn’t originating from the organic layer, but rather from the contamination of the metallic film.”

The study revealed when samples were properly encapsulated, no organic exchange bias was observed.

“It is very important to alert our peers in the scientific community of this negative result, as this research field data can be easily misinterpreted because of the very different nature of the elements involved in such devices,” said Meny. “This is important for developing the next generation of fully organic devices.”

Source: “Exchange bias at the organic/ferromagnet interface may not be a spinterface effect,” by Garen Avedissian, Jacek Arabski, Jennifer A. Wytko, Jean Weiss, Vasiliki Papaefthimiou, Guy Schmerber, Guillaume Rogez, Eric Beaurepaire, and Christian Meny, Applied Physics Reviews (2022). The article can be accessed at https://doi.org/10.1063/5.0054524 .