Tunable Exchange Bias in Hofmann MOF-Derived α-Fe2O3/Pt magnetic composites

The pursuit of strong, tunable, and thermally robust exchange bias (EB) is not only a fundamental scientific challenge but also a critical prerequisite for advancing spintronic technologies. Bottom-up designed nanostructures offer a versatile platform for engineering EB, owing to their precise control over composition, morphology, and assembly. However, studies on the EB effect in MOF-derived magnetic nanocomposites remains less unexplored. This study reports the EB effect in α-Fe2O3/Pt composites obtained via the pyrolysis of Hofmann-like Pt/Fe MOFs at 450 °C, 550 °C, and 650 °C. The results show that Pt particles are dispersed on the α-Fe2O3 particles, forming α-Fe2O3/Pt composites. The magnetic properties of samples are characterized by zero-field-cooled (ZFC) and field-cooled (FC) susceptibility as well as hysteresis loop measurements. Notably, a significant EB effect is observed in all samples and the optimized sample pyrolyzed at 450 °C exhibits the largest HEB of 2099 Oe at 2 K under a cooling field of 60 kOe, which exceeds that of pure α-Fe2O3 and other α-Fe2O3 based composites. These findings highlight calcination temperature as a critical parameter for tailoring EB effect in MOF-derived oxide/metal nanocomposites.