Discovery of magnetic field line dependent anisotropic chemiresistive response in magnetite: a new piece to the puzzle of magnetoreception.

Chemiresistive materials, which alter their electrical resistance in response to interactions with surrounding chemicals, are valued for their robustness, rapid detection ability and high sensitivity. Recent research has revealed that the sensing performance of these materials can be enhanced by applying an external magnetic field. In this study, we report a novel finding in the chemiresistive behaviour of magnetite (FeO), where its response has been found to be modulated in an anisotropic manner when exposed to an external magnetic field, analogous to Earth's magnetic field. Remarkably, substantial variations have been observed in response to analytes naturally present in the atmosphere. A remarkable increase in response was observed upon applying a 0.05 mT magnetic field, resulting in a more than 26-fold enhancement in sensitivity to relative humidity (98%), as well as a greater than 10-fold improvement in response to CO and a 25-fold increase in response to NO. This chemiresistive response exhibits a strong anisotropic dependence on the strength, direction and inclination of the magnetic field, suggesting that magnetite's electrical resistance dynamically adapts to both magnetic and chemical environmental changes. The observed behaviour under an Earth-like magnetic field closely mirrors the magnetoreception seen in biological species that rely on magnetite for navigation. This finding may provide new insights into the mechanisms behind magnetite-based magnetoreception observed in various biological species.